Vertebral Augmentation with Nitinol Endoprosthesis: Clinical Experience in 40 Patients with 1-Year Follow-up

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anselmetti, Giovanni Carlo, E-mail: gc.anselmetti@fastwebnet.it; Manca, Antonio, E-mail: anto.manca@gmail.com; Marcia, Stefano, E-mail: stemarcia@gmail.com

PurposeThis study was designed to assess the clinical outcomes of patients treated by vertebral augmentation with nitinol endoprosthesis (VNE) to treat painful vertebral compression fractures.MethodsForty patients with one or more painful osteoporotic VCF, confirmed by MRI and accompanied by back-pain unresponsive to a minimum 2 months of conservative medical treatment, underwent VNE at 42 levels. Preoperative and postoperative pain measured with Visual Analog Scale (VAS), disability measured by Oswestry Disability Index (ODI), and vertebral height restoration (measured with 2-dimensional reconstruction CT) were compared at last follow-up (average follow-up 15 months). Cement extravasation, subsequent fractures, and implant migration were recorded.ResultsLong-term follow-up was obtainedmore » in 38 of 40 patients. Both VAS and ODI significantly improved from a median of 8.0 (range 5–10) and 66 % (range 44–88 %) to 0.5 (range 0–8) and 6 % (range 6–66 %), respectively, at 1 year (p < 0.0001). Vertebral height measurements comparing time points increased in a statistically significant manner (ANOVA, p < 0.001). Overall cement extravasation rate was 9.5 %. Discal and venous leakage rates were 7.1 and 0 % respectively. No symptomatic extravasations occurred. Five of 38 (13.1 %) patients experienced new spontaneous, osteoporotic fractures. No device change or migration was observed.ConclusionsVNE is a safe and effective procedure that is able to provide long-lasting pain relief and durable vertebral height gain with a low rate of new fractures and cement leakages.« less

Elastoplasty: A Silicon Polymer as a New Filling Material for Kyphoplasty in Comparison to PMMA.

PubMed

Bornemann, Rahel; Rommelspacher, Yorck; Jansen, Tom R; Sander, Kirsten; Wirtz, Dieter C; Pflugmacher, Robert

2016-07-01

Painful vertebral compression fractures (VCF) caused by osteoporosis are a common health problem in the elderly population. If conservative treatments are unsuccessful, surgical treatments like vertebroplasty or kyphoplasty are recommended. But the use of Polymethylmethacrylat (PMMA) bone cement for augmentation surgery is associated with risks. Evaluation of the effectiveness and safety of a newly developed silicon polymer (VK100) that can be used instead of PMMA bone cement for kyphoplasty treatments. A retrospective study of 30 patients comparing the outcomes of kyphoplasty treatments conducted with PMMA and VK100. Clinic for Orthopedics and Trauma Surgery Bonn, Germany. Thirty patients with one to 3 VCF were treated either with balloon kyphoplasty using VK100 or balloon kyphoplasty using PMMA bone cement. Data from both groups was compared by a matched pair analysis. The medial vertebral height was measured at each examination radiologically. The patients stated their pain intensity using the Visual Analogue Scale (VAS) and the patient's functional impairment was evaluated with the Oswestry-Disability-Index (ODI).All data were assessed before surgery, and 3 days, 3 months, 6 months, and 12 months after surgery. Intraoperative and postoperative adverse events were documented. The patients' functional impairment and pain improved significantly after surgery. The course of ODI and VAS was comparable in both treatment groups, but the improvement in the VK group was significantly ongoing until the 12 month follow-up. Vertebral height improvement was significant in both groups, but the PMMA group achieved a better absolute restoration. The vertebral height stayed constant during the follow-up in the VK group and worsened significantly in the PMMA group. There was no significant difference between groups concerning the occurrence of additional fractures; and no other types of complications or surgery-related adverse events were observed in either the PMMA group or in the VK group. The study is only a matched pair analysis of 15 patients for each procedure and the amount of injected filling material was not recorded. The study results demonstrate that the clinical outcome of VAS and ODI of using the silicon polymer VK100 is comparable or slightly better than using PMMA. VK 100 shows a trend to minor additional fractures during the follow-up. However, height restoration is not satisfactory in comparison to PMMA, although vertebral height stayed more or less constant in the VK group. To address the augmentation success further, it would be necessary to study a larger patient group over a longer study period and to assess additional parameters such as bone density and injected amount of filling material.

Safety and Clinical Effectiveness of Percutaneous Vertebroplasty in the Elderly (≥80 years).

PubMed

Clarençon, Frédéric; Fahed, Robert; Gabrieli, Joseph; Guermazi, Yessine; Cormier, Evelyne; Molet-Benhamou, Luc; Jean, Betty; Dadoun, Sabrina; Rose, Michèle; Le Jean, Lise; Chiras, Jacques

2016-07-01

To evaluate the safety and clinical effectiveness of percutaneous vertebroplasty (PVP) in patients aged 80 and over. One hundred and seventy-three patients (127 women, 46 men; mean age = 84.2y) underwent 201 PVP procedures (391 vertebrae) in our institution from June 2008 to March 2012. One hundred and twenty-six patients (73 %) had osteoporotic vertebral compression fractures (VCF), 36 (20.5 %) were treated for tumour lesions, and the remaining 11 (6.5 %) for lesions from another cause. Comorbidities and American Society of Anesthesiologists (ASA) scores were assessed before treatment. Periprocedural and delayed complications were systematically recorded. A qualitative scale was used to evaluate pain relief at 1-month follow-up, ranging from significant pain worsening to marked improvement or disappearance. New fracture occurrence was assessed on follow-up imaging. Forty-five percent of patients had pretreatment ASA class scores ≥3. No major complication occurred. Pain was unchanged in 16.9 % of cases, mildly improved in 31.5 %, and disappeared in 47.8 %. We identified 27 (11 %) symptomatic new VCFs in patients with osteoporosis on follow-up imaging. The mean delay in diagnosis of new fractures was 5 ± 8.7 months. Even in the elderly, PVP remains a safe and effective technique for pain relief, independently of the underlying disease. • Post-PVP pain improvement was observed in 79.3 % of elderly patients. • PVP remains a safe technique in elderly patients. • No decompensation of comorbidity was observed in our series.

MODIS Tree Cover Validation for the Circumpolar Taiga-Tundra Transition Zone

NASA Technical Reports Server (NTRS)

Montesano, P. M.; Nelson, R.; Sun, G.; Margolis, H.; Kerber, A.; Ranson, K. J.

2009-01-01

A validation of the 2005 500m MODIS vegetation continuous fields (VCF) tree cover product in the circumpolar taiga-tundra ecotone was performed using high resolution Quickbird imagery. Assessing the VCF's performance near the northern limits of the boreal forest can help quantify the accuracy of the product within this vegetation transition area. The circumpolar region was divided into longitudinal zones and validation sites were selected in areas of varying tree cover where Quickbird imagery is available in Google Earth. Each site was linked to the corresponding VCF pixel and overlaid with a regular dot grid within the VCF pixel's boundary to estimate percent tree crown cover in the area. Percent tree crown cover was estimated using Quickbird imagery for 396 sites throughout the circumpolar region and related to the VCF's estimates of canopy cover for 2000-2005. Regression results of VCF inter-annual comparisons (2000-2005) and VCF-Quickbird image-interpreted estimates indicate that: (1) Pixel-level, inter-annual comparisons of VCF estimates of percent canopy cover were linearly related (mean R(sup 2) = 0.77) and exhibited an average root mean square error (RMSE) of 10.1 % and an average root mean square difference (RMSD) of 7.3%. (2) A comparison of image-interpreted percent tree crown cover estimates based on dot counts on Quickbird color images by two different interpreters were more variable (R(sup 2) = 0.73, RMSE = 14.8%, RMSD = 18.7%) than VCF inter-annual comparisons. (3) Across the circumpolar boreal region, 2005 VCF-Quickbird comparisons were linearly related, with an R(sup 2) = 0.57, a RMSE = 13.4% and a RMSD = 21.3%, with a tendency to over-estimate areas of low percent tree cover and anomalous VCF results in Scandinavia. The relationship of the VCF estimates and ground reference indicate to potential users that the VCF's tree cover values for individual pixels, particularly those below 20% tree cover, may not be precise enough to monitor 500m pixel-level tree cover in the taiga-tundra transition zone.

VCF-Explorer: filtering and analysing whole genome VCF files.

PubMed

Akgün, Mete; Demirci, Hüseyin

2017-11-01

The decreasing cost in high-throughput technologies led to a number of sequencing projects consisting of thousands of whole genomes. The paradigm shift from exome to whole genome brings a significant increase in the size of output files. Most of the existing tools which are developed to analyse exome files are not adequate for larger VCF files produced by whole genome studies. In this work we present VCF-Explorer, a variant analysis software capable of handling large files. Memory efficiency and avoiding computationally costly pre-processing step enable to carry out the analysis to be performed with ordinary computers. VCF-Explorer provides an easy to use environment where users can define various types of queries based on variant and sample genotype level annotations. VCF-Explorer can be run in different environments and computational platforms ranging from a standard laptop to a high performance server. VCF-Explorer is freely available at: http://vcfexplorer.sourceforge.net/. mete.akgun@tubitak.gov.tr. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

CircosVCF: circos visualization of whole-genome sequence variations stored in VCF files.

PubMed

Drori, E; Levy, D; Smirin-Yosef, P; Rahimi, O; Salmon-Divon, M

2017-05-01

Visualization of whole-genomic variations in a meaningful manner assists researchers in gaining new insights into the underlying data, especially when it comes in the context of whole genome comparisons. CircosVCF is a web based visualization tool for genome-wide variant data described in VCF files, using circos plots. The user friendly interface of CircosVCF supports an interactive design of the circles in the plot, and the integration of additional information such as experimental data or annotations. The provided visualization capabilities give a broad overview of the genomic relationships between genomes, and allow identification of specific meaningful SNPs regions. CircosVCF was implemented in JavaScript and is available at http://www.ariel.ac.il/research/fbl/software. malisa@ariel.ac.il. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Vegetation Continuous Fields--Transitioning from MODIS to VIIRS

NASA Astrophysics Data System (ADS)

DiMiceli, C.; Townshend, J. R.; Sohlberg, R. A.; Kim, D. H.; Kelly, M.

2015-12-01

Measurements of fractional vegetation cover are critical for accurate and consistent monitoring of global deforestation rates. They also provide important parameters for land surface, climate and carbon models and vital background data for research into fire, hydrological and ecosystem processes. MODIS Vegetation Continuous Fields (VCF) products provide four complementary layers of fractional cover: tree cover, non-tree vegetation, bare ground, and surface water. MODIS VCF products are currently produced globally and annually at 250m resolution for 2000 to the present. Additionally, annual VCF products at 1/20° resolution derived from AVHRR and MODIS Long-Term Data Records are in development to provide Earth System Data Records of fractional vegetation cover for 1982 to the present. In order to provide continuity of these valuable products, we are extending the VCF algorithms to create Suomi NPP/VIIRS VCF products. This presentation will highlight the first VIIRS fractional cover product: global percent tree cover at 1 km resolution. To create this product, phenological and physiological metrics were derived from each complete year of VIIRS 8-day surface reflectance products. A supervised regression tree method was applied to the metrics, using training derived from Landsat data supplemented by high-resolution data from Ikonos, RapidEye and QuickBird. The regression tree model was then applied globally to produce fractional tree cover. In our presentation we will detail our methods for creating the VIIRS VCF product. We will compare the new VIIRS VCF product to our current MODIS VCF products and demonstrate continuity between instruments. Finally, we will outline future VIIRS VCF development plans.

VCFR: A package to manipulate and visualize variant call format data in R

USDA-ARS?s Scientific Manuscript database

Software to call single nucleotide polymorphisms or related genetic variants has converged on the variant call format (vcf) as their output format of choice. This has created a need for tools to work with vcf files. While an increasing number of software exists to read vcf data, many of them only ex...

Compression fractures of the back

MedlinePlus

... treatments. Surgery can include: Balloon kyphoplasty Vertebroplasty Spinal fusion Other surgery may be done to remove bone ... Alternative Names Vertebral compression fractures; Osteoporosis - compression fracture Images Compression fracture References Cosman F, de Beur SJ, ...

cyvcf2: fast, flexible variant analysis with Python.

PubMed

Pedersen, Brent S; Quinlan, Aaron R

2017-06-15

Variant call format (VCF) files document the genetic variation observed after DNA sequencing, alignment and variant calling of a sample cohort. Given the complexity of the VCF format as well as the diverse variant annotations and genotype metadata, there is a need for fast, flexible methods enabling intuitive analysis of the variant data within VCF and BCF files. We introduce cyvcf2 , a Python library and software package for fast parsing and querying of VCF and BCF files and illustrate its speed, simplicity and utility. bpederse@gmail.com or aaronquinlan@gmail.com. cyvcf2 is available from https://github.com/brentp/cyvcf2 under the MIT license and from common python package managers. Detailed documentation is available at http://brentp.github.io/cyvcf2/. © The Author 2017. Published by Oxford University Press.

Trends in vena cava filter insertions and "prophylactic" use.

PubMed

Power, John R; Nakazawa, Kenneth R; Vouyouka, Ageliki G; Faries, Peter L; Egorova, Natalia N

2018-04-17

Prophylactic vena cava filter (VCF) use in patients without venous thromboembolism is common practice despite ongoing controversy. Thorough analysis of the evolution of this practice is lacking. We describe trends in VCF use and identify events associated with changes in practice. Using the National Inpatient Sample, we conducted a retrospective observational study of U.S. adult hospitalizations from 2000 to 2014. Trends in prophylactic VCF insertion were analyzed both across the entire study population and within subgroups according to trauma status and type of concurrent surgery. Annual percentage change (APC) was calculated, and trends were analyzed using Poisson regression. Among 461,904,314 adult inpatients (median [interquartile range] age, 58.1 [38.5-74.3] years; 39.6% male), the incidence of VCF insertion increased rapidly at first (from 0.19% to 0.35%; APC, 11.2%; 95% confidence interval [CI], 10.3%-12.2%; P < .001), then at a slower rate after the publication of the Prévention du Risque d'Embolie Pulmonaire par Interruption Cave 2 (PREPIC2) trial in 2005 (from 0.35% to 0.42%; APC, 4.4%; 95% CI, 2.8%-6.0%; P < .001), and it began decreasing after the 2010 Food and Drug Administration (FDA) safety alert (from 0.42% to 0.32%; APC, -5.5%; 95% CI, -6.5% to -4.6%; P < .001). The percentage of total VCFs that had a prophylactic indication increased quickly before publication of the PREPIC2 trial (APC, 19.5%; 95% CI, 17.9%-21.0%; P < .001), increased at a slower rate after publication in 2005 (APC, 4.4%; 95% CI, 2.6%-6.2%; P < .001), and dropped after the FDA safety alert, stabilizing at 18.5% for the last 3 years (APC, -0.3%; 95% CI, -2.2% to 1.7%; P = .8). Subgroups most associated with prophylactic VCF insertion were operative trauma (odds ratio [OR], 10.9; 95% CI, 10.2-11.7), orthopedic surgery (OR, 4.7; 95% CI, 4.3-5.2), and neurosurgical procedures (OR, 3.9; 95% CI, 3.6-4.2). All groups except orthopedic surgery experienced a deceleration in prophylactic VCF growth after the publication of PREPIC2. Meanwhile, the FDA safety alert was associated with a decrease in prophylactic VCF insertions for all groups except other major surgery. Whereas publication of the PREPIC2 trial led to a deceleration in prophylactic VCF insertion growth, the FDA alert had a bigger impact, leading to declining rates of prophylactic VCF use. Further investigations of prophylactic insertion of VCF in trauma, orthopedic, and neurosurgical patients are needed to determine whether current levels of use are justified. Copyright © 2018 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Hemodynamic Deterioration in Lateral Compression Pelvic Fracture After Prehospital Pelvic Circumferential Compression Device Application.

PubMed

Garner, Alan A; Hsu, Jeremy; McShane, Anne; Sroor, Adam

Increased fracture displacement has previously been described with the application of pelvic circumferential compression devices (PCCDs) in patients with lateral compression-type pelvic fracture. We describe the first reported case of hemodynamic deterioration temporally associated with the prehospital application of a PCCD in a patient with a complex acetabular fracture with medial displacement of the femoral head. Active hemorrhage from a site adjacent to the acetabular fracture was subsequently demonstrated on angiography. Caution in the application of PCCDs to patients with lateral compression-type fractures is warranted. Copyright © 2017 Air Medical Journal Associates. All rights reserved.

Biomechanical comparison of straight and helical compression plates for fixation of transverse and oblique bone fractures: Modeling and experiments.

PubMed

Sezek, Sinan; Aksakal, Bunyamin; Gürger, Murat; Malkoc, Melih; Say, Y

2016-08-12

Total deformation and stability of straight and helical compression plates were studied by means of the finite element method (FEM) and in vitro biomechanical experiments. Fixations of transverse (TF) and oblique (45°) bone (OF) fractures have been analyzed on sheep tibias by designing the straight compression (SP) and Helical Compression Plate (HP) models. The effects of axial compression, bending and torsion loads on both plating systems were analyzed in terms of total displacements. Numerical models and experimental models suggested that under compression loadings, bone fracture gap closures for both fracture types were found to be in the favor of helical plate designs. The helical plate (HP) fixations provided maximum torsional resistance compared to the (SP) fixations. The fracture gap closure and stability of helical plate fixation for transverse fractures was determined to be higher than that found for the oblique fractures. The comparison of average compression stress, bending and torsion moments showed that the FEM and experimental results are in good agreement and such designs are likely to have a positive impact in future bone fracture fixation designs.

Delayed Recognition of Thoracic and Lumbar Vertebral Compression Fractures in Minor Accident Cases.

PubMed

Hatgis, Jesse; Granville, Michelle; Jacobson, Robert E

2017-02-23

Osteoporotic vertebral compression fractures (VCFs) in the elderly are commonly diagnosed after a minor fall or trauma; however, the majority of these patients have either been previously evaluated for osteoporosis or are already under some form of medical treatment for osteoporosis at the time of the fall. Although accidents are a known cause of VCFs, these fractures are too often undiagnosed. In reviewing a group of patients seen after minor falls or automobile accidents who were complaining of general spine pain, we found a smaller subgroup with previously undiagnosed VCFs. These fractures were also the initial signs of a previously unrecognized osteoporotic process. Initial diagnosis, treatment, and therapy were usually focused on other spinal segments (i.e. mainly the lumbar spine) until both the VCF and the osteoporosis were identified. The purpose of this report is to raise awareness and discuss the steps for improved diagnosis of osteoporotic VCFs. A retrospective analysis was conducted on a large group of patients from one pain/accident clinic in a 24 month period. These patients were diagnosed with VCFs subsequent to the initial evaluation due to either persistent pain after conservative therapy or complaints of pain beyond the original injured area (i.e. typically the lumbar spine). At this point, a more detailed history was taken, including any past treatment for osteoporosis, or previous falls or injury to exclude the possibility of pre-existing fractures. A more focused examination of the painful area was completed, consisting of percussion at the fracture site identified on magnetic resonance imaging (MRI) or computed tomography (CT) scan. If possible, a bone scan was ordered to separate acute and subacute traumatic fractures from old/chronic fractures. Additionally, we surveyed two other similar pain/accident clinics who saw a comparable number and population of patients diagnosed with VCFs within a 24 month period to make a comparison of the number of VCFs they identified. Ten out of approximately 2700 patients seen over a 24 month period sustained acute thoracic or lumbar VCFs during a minor accident and were not previously diagnosed with osteoporosis. Since approximately 30% of the 2,700 patients had new accidents, 10 out of 800 new patients (1.25%) were found to have VCFs without a known history of osteoporosis. Two other surveyed pain/accident, clinics saw a similar number and population of patients in the same time period; however, each only diagnosed two or three VCFs while examining a similar number of patients in the clinic. In these two other clinics, a much lower percentage (0.3%) of patients were diagnosed with new VCFs. Awareness of the possibility of osteoporotic VCFs is the first step in detecting them. This study reveals the presence of a small but real risk of overlooking osteoporotic VCFs in minor trauma cases. When necessary, repeat or obtain better quality imaging in spinal segments affected by persistent pain. The thoracolumbar junction (i.e. T12 & L1 vertebrae) is especially at risk for sustaining VCFs. The delayed recognition of these VCFs and the patient's underlying osteoporosis after minor accident cases could present a major problem, as the critical time for patients to receive the proper medical or surgical treatments responsible for correcting and preventing further spinal deformity and pain has been reduced.

Brain anomalies in velo-cardio-facial syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitnick, R.J.; Bello, J.A.; Shprintzen, R.J.

Magnetic resonance imaging of the brain in 11 consecutively referred patients with velo-cardio-facial syndrome (VCF) showed anomalies in nine cases including small vermis, cysts adjacent to the frontal horns, and small posterior fossa. Focal signal hyperintensities in the white matter on long TR images were also noted. The nine patients showed a variety of behavioral abnormalities including mild development delay, learning disabilities, and characteristic personality traits typical of this common multiple anomaly syndrome which has been related to a microdeletion at 22q11. Analysis of the behavorial findings showed no specific pattern related to the brain anomalies, and the patients withmore » VCF who did not have detectable brain lesions also had behavioral abnormalities consistent with VCF. The significance of the lesions is not yet known, but the high prevalence of anomalies in this sample suggests that structural brain abnormalities are probably common in VCF. 25 refs.« less

Impact of Vegetation Cover Fraction Parameterization schemes on Land Surface Temperature Simulation in the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Lv, M.; Li, C.; Lu, H.; Yang, K.; Chen, Y.

2017-12-01

The parameterization of vegetation cover fraction (VCF) is an important component of land surface models. This paper investigates the impacts of three VCF parameterization schemes on land surface temperature (LST) simulation by the Common Land Model (CoLM) in the Tibetan Plateau (TP). The first scheme is a simple land cover (LC) based method; the second one is based on remote sensing observation (hereafter named as RNVCF) , in which multi-year climatology VCFs is derived from Moderate-resolution Imaging Spectroradiometer (MODIS) NDVI (Normalized Difference Vegetation Index); the third VCF parameterization scheme derives VCF from the LAI simulated by LSM and clump index at every model time step (hereafter named as SMVCF). Simulated land surface temperature(LST) and soil temperature by CoLM with three VCF parameterization schemes were evaluated by using satellite LST observation and in situ soil temperature observation, respectively, during the period of 2010 to 2013. The comparison against MODIS Aqua LST indicates that (1) CTL produces large biases for both four seasons in early afternoon (about 13:30, local solar time), while the mean bias in spring reach to 12.14K; (2) RNVCF and SMVCF reduce the mean bias significantly, especially in spring as such reduce is about 6.5K. Surface soil temperature observed at 5 cm depth from three soil moisture and temperature monitoring networks is also employed to assess the skill of three VCF schemes. The three networks, crossing TP from West to East, have different climate and vegetation conditions. In the Ngari network, located in the Western TP with an arid climate, there are not obvious differences among three schemes. In Naqu network, located in central TP with a semi-arid climate condition, CTL shows a severe overestimates (12.1 K), but such overestimations can be reduced by 79% by RNVCF and 87% by SMVCF. In the third humid network (Maqu in eastern TP), CoLM performs similar to Naqu. However, at both Naqu and Maqu networks, RNVCF shows significant overestimation in summer, perhaps due to RNVCF ignores the growing characteristics of vegetation (mainly grass) in these two regions. Our results demonstrate that VCF schemes have significant influence on LSM performance, and indicate that it is important to consider vegetation growing characteristics in VCF schemes for different LCs.

Compression fractures detection on CT

NASA Astrophysics Data System (ADS)

Bar, Amir; Wolf, Lior; Bergman Amitai, Orna; Toledano, Eyal; Elnekave, Eldad

2017-03-01

The presence of a vertebral compression fracture is highly indicative of osteoporosis and represents the single most robust predictor for development of a second osteoporotic fracture in the spine or elsewhere. Less than one third of vertebral compression fractures are diagnosed clinically. We present an automated method for detecting spine compression fractures in Computed Tomography (CT) scans. The algorithm is composed of three processes. First, the spinal column is segmented and sagittal patches are extracted. The patches are then binary classified using a Convolutional Neural Network (CNN). Finally a Recurrent Neural Network (RNN) is utilized to predict whether a vertebral fracture is present in the series of patches.

The effect of different torque wrenches on rotational stiffness in compressive femoral nails: a biomechanical study.

PubMed

Karaarslan, A A; Acar, N

2018-02-01

Rotation instability and locking screws failure are common problems. We aimed to determine optimal torque wrench offering maximum rotational stiffness without locking screw failure. We used 10 conventional compression nails, 10 novel compression nails and 10 interlocking nails with 30 composite femurs. We examined rotation stiffness and fracture site compression value by load cell with 3, 6 and 8 Nm torque wrenches using torsion apparatus with a maximum torque moment of 5 Nm in both directions. Rotational stiffness of composite femur-nail constructs was calculated. Rotational stiffness of composite femur-compression nail constructs compressed by 6 Nm torque wrench was 3.27 ± 1.81 Nm/angle (fracture site compression: 1588 N) and 60% more than that compressed with 3 Nm torque wrench (advised previously) with 2.04 ± 0.81 Nm/angle (inter fragmentary compression: 818 N) (P = 0.000). Rotational stiffness of composite-femur-compression nail constructs compressed by 3 Nm torque wrench was 2.04 ± 0.81 Nm/angle (fracture site compression: 818 N) and 277% more than that of interlocking nail with 0.54 ± 0.08 Nm/angle (fracture site compression: 0 N) (P = 0.000). Rotational stiffness and fracture site compression value produced by 3 Nm torque wrench was not satisfactory. To obtain maximum rotational stiffness and fracture site compression value without locking screw failure, 6 Nm torque wrench in compression nails and 8 Nm torque wrench in novel compression nails should be used.

Analysis of 22q11.2 deletions by FISH in a series of velocardiofacial syndrome patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ravnan, J.B.; Golabi, M.; Lebo, R.V.

Deletions in chromosome 22 band q11.2 have been associated with velocardiofacial (VCF or Shprintzen) syndrome and the DiGeorge anomaly. A study of VCF patients evaluated at the UCSF Medical Center was undertaken to correlate disease phenotype with presence or absence of a deletion. Patients referred for this study had at least two of the following: dysmorphic facial features, frequent ear infections or hearing loss, palate abnormalities, thymic hypoplasia, hypocalcemia, congenital heart defect, hypotonia, and growth or language delay. Fluorescence in situ hybridization (FISH) using the DiGeorge critical region probe N25 was used to classify patients according to the presence ormore » absence of a deletion in 22q11.2, and the results were compared to clinical characteristics. We have completed studies on 58 patients with features of VCF. Twenty-one patients (36%) were found to have a deletion in 22q11.2 by FISH. A retrospective study of archived slides from 14 patients originally studied only by prometaphase GTG banding found six patients had a deletion detected by FISH; of these, only two had a microscopically visible chromosome deletion. Our study of 11 sets of parents of children with the deletion found two clinically affected mothers with the deletion, including one with three of three children clinically affected. A few patients who did not fit the classical VCF description had a 22q11.2 deletion detected by FISH. These included one patient with both cleft lip and palate, and another with developmental delay and typical facial features but no cardiac or palate abnormalities. Both patients with the DiGeorge anomaly as part of VCF had the deletion. On the other hand, a number of patients diagnosed clinically with classical VCF did not have a detectable deletion. This raises the question whether they represent a subset of patients with a defect of 22q11.2 not detected by the N25 probe, or whether they represent a phenocopy of VCF.« less

Usefulness of prone cross-table lateral radiographs in vertebral compression fractures.

PubMed

Cho, Jae Hwan; Shin, Sang Ik; Lee, Jae Hyup; Yeom, Jin Sup; Chang, Bong-Soon; Lee, Choon-Ki

2013-09-01

Dynamic radiographs are recommended to investigate non-healing evidence such as the dynamic mobility or intravertebral clefts in osteoporotic vertebral compression fractures (VCFs). However, it is difficult to examine standing flexion and extension lateral radiographs due to severe pain. The use of prone cross-table lateral radiographs (PrLRs) as a diagnostic tool has never been proposed to our knowledge. The purpose of this study is to clarify the usefulness of PrLRs in diagnosis and treatment of VCFs. We reviewed 62 VCF patients examined with PrLRs between January 1, 2008 and June 30, 2011. To compare the degree of pain provoked between standing extension lateral radiographs (StLRs) and PrLRs, numeric rating scale (NRS) scores were assessed and compared by a paired t-test. Vertebroplasty was done for 40 patients and kyphoplasty was done for 9 patients with routine manners. To assess the degree of postural reduction, vertebral wedge angles (VWA) and vertebral height ratios (VHR) were calculated by using preoperative StLRs, PrLRs, and postoperative lateral radiographs. Two variables derived from changes in VWA and VHR between preoperative and postoperative radiographs were compared by a paired t-test. The average NRS scores were 6.23 ± 1.67 in StLRs and 5.18 ± 1.47 in PrLRs. The degree of pain provocation was lower in using PrLRs than StLRs (p < 0.001). The average changes of VWA between preoperative and postoperative status were 5.24° ± 6.16° with PrLRs and 3.46° ± 3.47° with StLRs. The average changes of VHR were 0.248 ± 0.178 with PrLRs and 0.148 ± 0.161 with StLRs. The comparisons by two variables showed significant differences for both parameters (p = 0.021 and p < 0.001, respectively). The postoperative radiological status was reflected more precisely when using PrLRs than StLRs. In comparison with StLR, the PrLR was more accurate in predicting the degree of restoration of postoperative vertebral heights and wedge angles, and provoked less pain during examination. The PrLR could be a useful diagnostic tool to detect intravertebral cleft or intravertebral dynamic instability.

[Compression fracture of a fragile lumbar vertebrae as a cause of low back pain].

PubMed

Ostojić, Zdenko; Ostojić, Ljerka; Pehar, Zoran; Ceramida, Meliha; Letica, Ludvih

2002-01-01

The patient felt sharp back lumbal pain while lifting heavy object in flexion position of the back. Rtg showed compressive fracture of L2. MRI showed secondary posttraumatic edema around compressive fracture of the body of L2. The compressive fracture was caused by intracorporal haemangiome of L2. After six months we had spontaneous sanation of heamgiome. Regarding to the therapy only electromagnetotherapy was used as well as programme of kinezitherapy given according to the condition of the body of L2.

Avalanches in compressed Ti-Ni shape-memory porous alloys: An acoustic emission study.

PubMed

Soto-Parra, Daniel; Zhang, Xiaoxin; Cao, Shanshan; Vives, Eduard; Salje, Ekhard K H; Planes, Antoni

2015-06-01

Mechanical avalanches during compression of martensitic porous Ti-Ni have been characterized by high-frequency acoustic emission (AE). Two sequences of AE signals were found in the same sample. The first sequence is mainly generated by detwinning at the early stages of compression while fracture dominates the later stages. Fracture also determines the catastrophic failure (big crash). For high-porosity samples, the AE energies of both sequences display power-law distributions with exponents ɛ≃2 (twinning) and 1.7 (fracture). The two power laws confirm that twinning and fracture both lead to avalanche criticality during compression. As twinning precedes fracture, the observation of twinning allows us to predict incipient fracture of the porous shape memory material as an early warning sign (i.e., in bone implants) before the fracture collapse actually happens.

The tolerance of the femoral shaft in combined axial compression and bending loading.

PubMed

Ivarsson, B Johan; Genovese, Daniel; Crandall, Jeff R; Bolton, James R; Untaroiu, Costin D; Bose, Dipan

2009-11-01

The likelihood of a front seat occupant sustaining a femoral shaft fracture in a frontal crash has traditionally been assessed by an injury criterion relying solely on the axial force in the femur. However, recently published analyses of real world data indicate that femoral shaft fracture occurs at axial loads levels below those found experimentally. One hypothesis attempting to explain this discrepancy suggests that femoral shaft fracture tends to occur as a result of combined axial compression and applied bending. The current study aims to evaluate this hypothesis by investigating how these two loading components interact. Femoral shafts harvested from human cadavers were loaded to failure in axial compression, sagittal plane bending, and combined axial compression and sagittal plane bending. All specimens subjected to bending and combined loading fractured midshaft, whereas the specimens loaded in axial compression demonstrated a variety of failure locations including midshaft and distal end. The interaction between the recorded levels of applied moment and axial compression force at fracture were evaluated using two different analysis methods: fitting of an analytical model to the experimental data and multiple regression analysis. The two analysis methods yielded very similar relationships between applied moment and axial compression force at midshaft fracture. The results indicate that posteroanterior bending reduces the tolerance of the femoral shaft to axial compression and that that this type of combined loading therefore may contribute to the high prevalence of femoral shaft fracture in frontal crashes.

Impact of consensus statements and reimbursement on vena cava filter utilization.

PubMed

Desai, Sapan S; Naddaf, Abdallah; Pan, James; Hood, Douglas; Hodgson, Kim J

2016-08-01

Pulmonary embolism is the third most common cause of death in hospitalized patients. Vena cava filters (VCFs) are indicated in patients with venous thromboembolism with a contraindication to anticoagulation. Prophylactic indications are still controversial. However, the utilization of VCFs during the past 15 years may have been affected by societal recommendations and reimbursement rates. The aim of this study was to evaluate the impact of societal guidelines and reimbursement on national trends in VCF placement from 1998 to 2012. The National Inpatient Sample was used to identify patients who underwent VCF placement between 1998 and 2012. VCF placement yearly rates were evaluated. Societal guidelines and consensus statements were identified using a PubMed search. Reimbursement rates for VCF were determined on the basis of published Medicare reports. Statistical analysis was completed using descriptive statistics, Fisher exact test, and trend analysis using the Mann-Kendall test and considered significant for P < .05. The use of VCFs increased 350% between January 1998 and January 2008. Consensus statements in favor of VCFs published by the Eastern Association for the Surgery of Trauma (July 2002) and the Society of Interventional Radiology (March 2006) were temporally associated with a significant 138% and 122% increase in the use of VCFs, respectively (P = .014 and P = .023, respectively). The American College of Chest Physicians guidelines (February 2008 and 2012) discouraging the use of VCFs were preceded by an initial stabilization in the use of VCFs between 2008 and 2012, followed by a 16% decrease in use starting in March 2012 (P = .38). Changes in Medicare reimbursement were not followed by a change in VCF implantation rates. There is a temporal association between the societal guidelines' recommendations regarding VCF placement and the actual rates of insertion. More uniform consensus statements from multiple societies along with the use of level I evidence may be required to lead to a definitive change in practice. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Three Cases of Spine Fractures after an Airplane Crash.

PubMed

Lee, Han Joo; Moon, Bong Ju; Pennant, William A; Shin, Dong Ah; Kim, Keung Nyun; Yoon, Do Heum; Ha, Yoon

2015-10-01

While injuries to the spine after an airplane crash are not rare, most crashes result in fatal injuries. As such, few studies exist that reported on spine fractures sustained during airplane accidents. In this report, we demonstrate three cases of spine fractures due to crash landing of a commercial airplane. Three passengers perished from injuries after the crash landing, yet most of the passengers and crew on board survived, with injuries ranging from minor to severe. Through evaluating our three spine fracture patients, it was determined that compression fracture of the spine was the primary injury related to the airplane accident. The first patient was a 20-year-old female who sustained a T6-8 compression fracture without neurologic deterioration. The second patient was a 33-year-old female with an L2 compression fracture, and the last patient was a 49-year-old male patient with a T8 compression fracture. All three patients were managed conservatively and required spinal orthotics. During the crash, each of these patients were subjected to direct, downward high gravity z-axis (Gz) force, which gave rise to load on the spine vertically, thereby causing compression fracture. Therefore, new safety methods should be developed to prevent excessive Gz force during airplane crash landings.

Three Cases of Spine Fractures after an Airplane Crash

PubMed Central

Lee, Han Joo; Moon, Bong Ju; Pennant, William A.; Shin, Dong Ah; Kim, Keung Nyun; Yoon, Do Heum

2015-01-01

While injuries to the spine after an airplane crash are not rare, most crashes result in fatal injuries. As such, few studies exist that reported on spine fractures sustained during airplane accidents. In this report, we demonstrate three cases of spine fractures due to crash landing of a commercial airplane. Three passengers perished from injuries after the crash landing, yet most of the passengers and crew on board survived, with injuries ranging from minor to severe. Through evaluating our three spine fracture patients, it was determined that compression fracture of the spine was the primary injury related to the airplane accident. The first patient was a 20-year-old female who sustained a T6-8 compression fracture without neurologic deterioration. The second patient was a 33-year-old female with an L2 compression fracture, and the last patient was a 49-year-old male patient with a T8 compression fracture. All three patients were managed conservatively and required spinal orthotics. During the crash, each of these patients were subjected to direct, downward high gravity z-axis (Gz) force, which gave rise to load on the spine vertically, thereby causing compression fracture. Therefore, new safety methods should be developed to prevent excessive Gz force during airplane crash landings. PMID:27169094

Fracture mechanisms and fracture control in composite structures

NASA Astrophysics Data System (ADS)

Kim, Wone-Chul

Four basic failure modes--delamination, delamination buckling of composite sandwich panels, first-ply failure in cross-ply laminates, and compression failure--are analyzed using linear elastic fracture mechanics (LEFM) and the J-integral method. Structural failures, including those at the micromechanical level, are investigated with the aid of the models developed, and the critical strains for crack propagation for each mode are obtained. In the structural fracture analyses area, the fracture control schemes for delamination in a composite rib stiffener and delamination buckling in composite sandwich panels subjected to in-plane compression are determined. The critical fracture strains were predicted with the aid of LEFM for delamination and the J-integral method for delamination buckling. The use of toughened matrix systems has been recommended for improved damage tolerant design for delamination crack propagation. An experimental study was conducted to determine the onset of delamination buckling in composite sandwich panel containing flaws. The critical fracture loads computed using the proposed theoretical model and a numerical computational scheme closely followed the experimental measurements made on sandwich panel specimens of graphite/epoxy faceskins and aluminum honeycomb core with varying faceskin thicknesses and core sizes. Micromechanical models of fracture in composites are explored to predict transverse cracking of cross-ply laminates and compression fracture of unidirectional composites. A modified shear lag model which takes into account the important role of interlaminar shear zones between the 0 degree and 90 degree piles in cross-ply laminate is proposed and criteria for transverse cracking have been developed. For compressive failure of unidirectional composites, pre-existing defects play an important role. Using anisotropic elasticity, the stress state around a defect under a remotely applied compressive load is obtained. The experimentally observed complex compressive failure modes, such as shear crippling and pure compressive fiber failure of fibers are explained by the predicted stress distributions calculated in this work. These fracture analyses can be damage tolerant design methodology for composite structures. The proposed fracture criteria and the corresponding critical fracture strains provide the designer with quantitative guidelines for safe-life design. These have been incorporated into a fracture control plan for composite structures, which is also described. Currently, fracture control plans do not exist for composite structures; the proposed plan is a first step towards establishing fracture control and damage tolerant design methodology for this important class of materials.

Torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis).

PubMed

Kerrigan, Shannon M; Kapatkin, Amy S; Garcia, Tanya C; Robinson, Duane A; Guzman, David Sanchez-Migallon; Stover, Susan M

2018-04-01

OBJECTIVE To describe the torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis). SAMPLE 16 cadaveric tibiotarsal bones from 8 red-tailed hawks. PROCEDURES 1 tibiotarsal bone from each bird was randomly assigned to be tested in torsion, and the contralateral bone was tested in axial compression. Intact bones were monotonically loaded in either torsion (n = 8) or axial compression (8) to failure. Mechanical variables were derived from load-deformation curves. Fracture configurations were described. Effects of sex, limb side, and bone dimensions on mechanical properties were assessed with a mixed-model ANOVA. Correlations between equivalent torsional and compressive properties were determined. RESULTS Limb side and bone dimensions were not associated with any mechanical property. During compression tests, mean ultimate cumulative energy and postyield energy for female bones were significantly greater than those for male bones. All 8 bones developed a spiral diaphyseal fracture and a metaphyseal fissure or fracture during torsional tests. During compression tests, all bones developed a crushed metaphysis and a fissure or comminuted fracture of the diaphysis. Positive correlations were apparent between most yield and ultimate torsional and compressive properties. CONCLUSIONS AND CLINICAL RELEVANCE The torsional and axial compressive properties of tibiotarsal bones described in this study can be used as a reference for investigations into fixation methods for tibiotarsal fractures in red-tailed hawks. Although the comminuted and spiral diaphyseal fractures induced in this study were consistent with those observed in clinical practice, the metaphyseal disruption observed was not and warrants further research.

Method for selectively orienting induced fractures in subterranean earth formations

DOEpatents

Shuck, Lowell Z.

1977-02-01

The orientation of hydraulically-induced fractures in relatively deep subterranean earth formations is normally confined to vertical projections along a plane parallel to the maximum naturally occurring (tectonic) compressive stress field. It was found that this plane of maximum compressive stress may be negated and, in effect, re-oriented in a plane projecting generally orthogonal to the original tectonic stress plane by injecting liquid at a sufficiently high pressure into a wellbore fracture oriented in a plane parallel to the plane of tectonic stress for the purpose of stressing the surrounding earth formation in a plane generally orthogonal to the plane of tectonic stress. With the plane of maximum compressive stress re-oriented due to the presence of the induced compressive stress, liquid under pressure is injected into a second wellbore disposed within the zone influenced by the induced compressive stress but at a location in the earth formation laterally spaced from the fracture in the first wellbore for effecting a fracture in the second wellbore along a plane generally orthogonal to the fracture in the first wellbore.

Large liquid rocket engine transient performance simulation system

NASA Technical Reports Server (NTRS)

Mason, J. R.; Southwick, R. D.

1989-01-01

Phase 1 of the Rocket Engine Transient Simulation (ROCETS) program consists of seven technical tasks: architecture; system requirements; component and submodel requirements; submodel implementation; component implementation; submodel testing and verification; and subsystem testing and verification. These tasks were completed. Phase 2 of ROCETS consists of two technical tasks: Technology Test Bed Engine (TTBE) model data generation; and system testing verification. During this period specific coding of the system processors was begun and the engineering representations of Phase 1 were expanded to produce a simple model of the TTBE. As the code was completed, some minor modifications to the system architecture centering on the global variable common, GLOBVAR, were necessary to increase processor efficiency. The engineering modules completed during Phase 2 are listed: INJTOO - main injector; MCHBOO - main chamber; NOZLOO - nozzle thrust calculations; PBRNOO - preburner; PIPE02 - compressible flow without inertia; PUMPOO - polytropic pump; ROTROO - rotor torque balance/speed derivative; and TURBOO - turbine. Detailed documentation of these modules is in the Appendix. In addition to the engineering modules, several submodules were also completed. These submodules include combustion properties, component performance characteristics (maps), and specific utilities. Specific coding was begun on the system configuration processor. All functions necessary for multiple module operation were completed but the SOLVER implementation is still under development. This system, the Verification Checkout Facility (VCF) allows interactive comparison of module results to store data as well as provides an intermediate checkout of the processor code. After validation using the VCF, the engineering modules and submodules were used to build a simple TTBE.

Management of vertebral compression fracture in general practice: BEACH program.

PubMed

Megale, Rodrigo Z; Pollack, Allan; Britt, Helena; Latimer, Jane; Naganathan, Vasi; McLachlan, Andrew J; Ferreira, Manuela L

2017-01-01

The pain associated with vertebral compression fractures can cause significant loss of function and quality of life for older adults. Despite this, there is little consensus on how best to manage this condition. To describe usual care provided by general practitioners (GPs) in Australia for the management of vertebral compression fractures. Data from the Bettering the Evaluation And Care of Health (BEACH) program collected between April 2005 and March 2015 was used for this study. Each year, a random sample of approximately 1,000 GPs each recorded information on 100 consecutive encounters. We selected those encounters at which vertebral compression fracture was managed. Analyses of management options were limited to encounters with patients aged 50 years or over. i) patient demographics; ii) diagnoses/problems managed; iii) the management provided for vertebral compression fracture during the encounter. Robust 95% confidence intervals, adjusted for the cluster survey design, were used to assess significant differences between group means. Vertebral compression fractures were managed in 211 (0.022%; 95% CI: 0.018-0.025) of the 977,300 BEACH encounters recorded April 2005- March 2015. That provides a national annual estimate of 26,000 (95% CI: 22,000-29,000) encounters at which vertebral fractures were managed. At encounters with patients aged 50 years or over (those at higher risk of primary osteoporosis), prescription of analgesics was the most common management action, particularly opioids analgesics (47.1 per 100 vertebral fractures; 95% CI: 38.4-55.7). Prescriptions of paracetamol (8.2; 95% CI: 4-12.4) or non-steroidal anti-inflammatory drugs (4.1; 95% CI: 1.1-7.1) were less frequent. Non-pharmacological treatment was provided at a rate of 22.4 per 100 vertebral fractures (95% CI: 14.6-30.1). At least one referral (to hospital, specialist, allied health care or other) was given for 12.3 per 100 vertebral fractures (95% CI: 7.8-16.8). The prescription of oral opioid analgesics remains the common general practice approach for vertebral compression fractures management, despite the lack of evidence to support this. Clinical trials addressing management of these fractures are urgently needed to improve the quality of care patients receive.

Molecular motions that shape the cardiac action potential: Insights from voltage clamp fluorometry.

PubMed

Zhu, Wandi; Varga, Zoltan; Silva, Jonathan R

2016-01-01

Very recently, voltage-clamp fluorometry (VCF) protocols have been developed to observe the membrane proteins responsible for carrying the ventricular ionic currents that form the action potential (AP), including those carried by the cardiac Na(+) channel, NaV1.5, the L-type Ca(2+) channel, CaV1.2, the Na(+)/K(+) ATPase, and the rapid and slow components of the delayed rectifier, KV11.1 and KV7.1. This development is significant, because VCF enables simultaneous observation of ionic current kinetics with conformational changes occurring within specific channel domains. The ability gained from VCF, to connect nanoscale molecular movement to ion channel function has revealed how the voltage-sensing domains (VSDs) control ion flux through channel pores, mechanisms of post-translational regulation and the molecular pathology of inherited mutations. In the future, we expect that this data will be of great use for the creation of multi-scale computational AP models that explicitly represent ion channel conformations, connecting molecular, cell and tissue electrophysiology. Here, we review the VCF protocol, recent results, and discuss potential future developments, including potential use of these experimental findings to create novel computational models. Copyright © 2015 Elsevier Ltd. All rights reserved.

Pelvic crescent fractures: variations in injury mechanism and radiographic pattern.

PubMed

Gehlert, Rick J; Xing, Zhiqing; DeCoster, Thomas A

2014-01-01

Pelvic crescent fracture, also known as sacroiliac fracture-dislocation, is traditionally considered as a lateral compression injury and a vertically stable injury. Thirty consecutive cases were analyzed and it was found that 63% of cases were caused by lateral compression (LC), 27% by anteroposterior compression (APC), and 10% by vertical shear (VS). APC and VS injuries cause significant displacement of the anterior iliac fragment, but 21% of LC injury cases showed minimal displacement and were treated successfully with nonoperative treatment. Different injury mechanisms also produce different types of pelvic instability. More important, different injury mechanisms produce distinct radiographic fracture patterns regarding the obliquity of the fracture line and fracture surface. These differences in the fracture pattern will influence the decision of internal fixation options. Therefore, treatment of pelvic crescent fractures should be based on individual analysis of injury mechanism and radiographic fracture pattern.

Effect of rock rheology on fluid leak- off during hydraulic fracturing

NASA Astrophysics Data System (ADS)

Yarushina, V. M.; Bercovici, D.; Oristaglio, M. L.

2012-04-01

In this communication, we evaluate the effect of rock rheology on fluid leak­off during hydraulic fracturing of reservoirs. Fluid leak-off in hydraulic fracturing is often nonlinear. The simple linear model developed by Carter (1957) for flow of fracturing fluid into a reservoir has three different regions in the fractured zone: a filter cake on the fracture face, formed by solid additives from the fracturing fluid; a filtrate zone affected by invasion of the fracturing fluid; and a reservoir zone with the original formation fluid. The width of each zone, as well as its permeability and pressure drop, is assumed to remain constant. Physical intuition suggests some straightforward corrections to this classical theory to take into account the pressure dependence of permeability, the compressibility or non-Newtonian rheology of fracturing fluid, and the radial (versus linear) geometry of fluid leak­off from the borehole. All of these refinements, however, still assume that the reservoir rock adjacent to the fracture face is non­deformable. Although the effect of poroelastic stress changes on leak-off is usually thought to be negligible, at the very high fluid pressures used in hydraulic fracturing, where the stresses exceed the rock strength, elastic rheology may not be the best choice. For example, calculations show that perfectly elastic rock formations do not undergo the degree of compaction typically seen in sedimentary basins. Therefore, pseudo-elastic or elastoplastic models are used to fit observed porosity profiles with depth. Starting from balance equations for mass and momentum for fluid and rock, we derive a hydraulic flow equation coupled with a porosity equation describing rock compaction. The result resembles a pressure diffusion equation with the total compressibility being a sum of fluid, rock and pore-space compressibilities. With linear elastic rheology, the bulk formation compressibility is dominated by fluid compressibility. But the possibility of permanent, time-independent (plastic) rock deformation significantly increases the pore space compressibility (compaction), which becomes a leading term in the total compressibility. Inclusion of rock and fluid compressibilities in the model can explain both linear and nonlinear leak­off. In particular, inclusion of rock compaction and decompaction may be important for description of naturally fractured and tight gas reservoirs for which very strong dependence of permeability on porosity has been reported. Carter R.D. Derivation of the general equation for estimating the extent of the fractured area. Appendix I of "Optimum fluid characteristics for fracture extension", Drilling and Production Practice, G.C. Howard and C.R.Fast, New York, New York, USA, American Petroleum Institute (1957), 261-269.

Assessing Impact Direction in 3-point Bending of Human Femora: Incomplete Butterfly Fractures and Fracture Surfaces,.

PubMed

Isa, Mariyam I; Fenton, Todd W; Deland, Trevor; Haut, Roger C

2018-01-01

Current literature associates bending failure with butterfly fracture, in which fracture initiates transversely at the tensile surface of a bent bone and branches as it propagates toward the impact surface. The orientation of the resulting wedge fragment is often considered diagnostic of impact direction. However, experimental studies indicate bending does not always produce complete butterfly fractures or produces wedge fragments variably in tension or compression, precluding their use in interpreting directionality. This study reports results of experimental 3-point bending tests on thirteen unembalmed human femora. Complete fracture patterns varied following bending failure, but incomplete fractures and fracture surface characteristics were observed in all impacted specimens. A flat, billowy fracture surface was observed in tension, while jagged, angular peaks were observed in compression. Impact direction was accurately reconstructed using incomplete tension wedge butterfly fractures and tension and compression fracture surface criteria in all thirteen specimens. © 2017 American Academy of Forensic Sciences.

Practical use of bone scan in patients with an osteoporotic vertebral compression fracture.

PubMed

Jun, Deuk Soo; An, Byoung Keun; Yu, Chang Hun; Hwang, Kyung Hoon; Paik, Je Won

2015-02-01

Rib fractures are one of main causes of chest or flank pain when related to an osteoporotic vertebral compression fracture (OVCF). The authors investigated the incidence and risk factors of rib fracture in 284 patients with OVCF using bone scans and evaluated the feasibility as to whether bone scans could be utilized as a useful screening tool. Hot uptake lesions on ribs were found in 122 cases (43.0%). The factors analyzed were age, sex, number and locations of fractured vertebrae, BMD, and compression rates as determined using initial radiography. However, no statistical significances were found. In 16 cases (5.6%), there were concurrent multiple fractures of both the thoracic and lumbar spines not detected by single site MRI. Sixty cases (21.1%) of OVCF with the a compression rate of less than 15% could not be identified definitely by initial plain radiography, but were confirmed by bone scans. It is concluded that a bone scan has outstanding ability for the screening of rib fractures associated with OVCF. Non-adjacent multiple fractures in both thoracic and lumbar spines and fractures not identified definitely by plain radiography were detected on bone scans, which provided a means for determining management strategies and predicting prognosis.

Previous vertebral compression fractures add to the deterioration of the disability and quality of life after an acute compression fracture.

PubMed

Suzuki, Nobuyuki; Ogikubo, Osamu; Hansson, Tommy

2010-04-01

Prevalent vertebral compression fracture(s) have been reported as having a negative impact on pain, disability, and quality of life. But no study has evaluated the effect of previous fracture on the course of acute compression fractures. The aim of the present study was to compare the natural course of the acute compression fracture in patients with (n = 51) and without (n = 56) previous vertebral compression fracture(s). The study is a retrospective analysis of a prospective cohort followed with postal questionnaires during a 12-month period after an acute fracture event. Eligible patients were those over 40 years of age, who were admitted to the emergency unit because of back pain and had an X-ray confirmed acute vertebral body fracture. A total of 107 patients were included in the study. The pain, disability (von Korff pain and disability scores), ADL (Hannover ADL score), and quality of life (QoL) (EQ-5D) were measured after 3 weeks, and 3, 6, and 12 months. The X-rays from the first visit to the emergency unit were evaluated. The difference of the scores between the groups with and without previous fracture was statistically significant (P < 0.05) at 3 weeks, 6 and 12 months for von Korff disability score, at all occasions for EQ-5D and at 3-12 months for Hannover ADL score, but only at 12 months for the von Korff pain intensity score. In both the groups all scores had improved in a statistically significant way at 3 months. The number of previous fractures was related to all the outcome scores in a statistically significant way (P < 0.05) except von Korff pain intensity score at 3 weeks and 3 months and von Korff disability score at 3 months. In conclusion, disability, ADL, and QoL scores, but not pain intensity score, were significantly worse in the patients with previous fracture from the fracture episode through the first 12 months. However, the improvements during the follow-up year seen in both groups were of a similar magnitude. The presence or absence of a previous fracture in an acutely fractured patient will influence the prognosis and thus possibly also the indications for treatments.

Biomechanical comparison of straight DCP and helical plates for fixation of transverse and oblique bone fractures.

PubMed

Aksakal, Bunyamin; Gurger, Murat; Say, Yakup; Yilmaz, Erhan

2014-01-01

Biomechanical comparison of straight DCP and helical plates for fixation of transversal and oblique tibial bone fractures were analyzed and compared to each other by axial compression, bending and torsion tests. An in vitro osteosynthesis of transverse (TF) and oblique bone fracture (OF) fixations have been analysed on fresh sheep tibias by using the DCP and helical compression plates (HP). Statistically significant differences were found for both DCP and helical plate fixations under axial compression, bending and torsional loads. The strength of fixation systems was in favor of DC plating with exception of the TF-HP fixation group under compression loads and torsional moments. The transvers fracture (TF) stability was found to be higher than that found in oblique fracture (OF) fixed by helical plates (HP). However, under torsional testing, compared to conventional plating, the helical plate fixations provided a higher torsional resistance and strength. The maximum stiffness at axial compression loading and maximum torsional strength was achieved in torsional testing for the TF-HP fixations. From in vitro biomechanical analysis, fracture type and plate fixation system groups showed different responses under different loadings. Consequently, current biomechanical analyses may encourage the usage of helical HP fixations in near future during clinical practice for transverse bone fractures.

Optimized distributed systems achieve significant performance improvement on sorted merging of massive VCF files.

PubMed

Sun, Xiaobo; Gao, Jingjing; Jin, Peng; Eng, Celeste; Burchard, Esteban G; Beaty, Terri H; Ruczinski, Ingo; Mathias, Rasika A; Barnes, Kathleen; Wang, Fusheng; Qin, Zhaohui S

2018-06-01

Sorted merging of genomic data is a common data operation necessary in many sequencing-based studies. It involves sorting and merging genomic data from different subjects by their genomic locations. In particular, merging a large number of variant call format (VCF) files is frequently required in large-scale whole-genome sequencing or whole-exome sequencing projects. Traditional single-machine based methods become increasingly inefficient when processing large numbers of files due to the excessive computation time and Input/Output bottleneck. Distributed systems and more recent cloud-based systems offer an attractive solution. However, carefully designed and optimized workflow patterns and execution plans (schemas) are required to take full advantage of the increased computing power while overcoming bottlenecks to achieve high performance. In this study, we custom-design optimized schemas for three Apache big data platforms, Hadoop (MapReduce), HBase, and Spark, to perform sorted merging of a large number of VCF files. These schemas all adopt the divide-and-conquer strategy to split the merging job into sequential phases/stages consisting of subtasks that are conquered in an ordered, parallel, and bottleneck-free way. In two illustrating examples, we test the performance of our schemas on merging multiple VCF files into either a single TPED or a single VCF file, which are benchmarked with the traditional single/parallel multiway-merge methods, message passing interface (MPI)-based high-performance computing (HPC) implementation, and the popular VCFTools. Our experiments suggest all three schemas either deliver a significant improvement in efficiency or render much better strong and weak scalabilities over traditional methods. Our findings provide generalized scalable schemas for performing sorted merging on genetics and genomics data using these Apache distributed systems.

Isomorphic semantic mapping of variant call format (VCF2RDF).

PubMed

Penha, Emanuel Diego S; Iriabho, Egiebade; Dussaq, Alex; de Oliveira, Diana Magalhães; Almeida, Jonas S

2017-02-15

The move of computational genomics workflows to Cloud Computing platforms is associated with a new level of integration and interoperability that challenges existing data representation formats. The Variant Calling Format (VCF) is in a particularly sensitive position in that regard, with both clinical and consumer-facing analysis tools relying on this self-contained description of genomic variation in Next Generation Sequencing (NGS) results. In this report we identify an isomorphic map between VCF and the reference Resource Description Framework. RDF is advanced by the World Wide Web Consortium (W3C) to enable representations of linked data that are both distributed and discoverable. The resulting ability to decompose VCF reports of genomic variation without loss of context addresses the need to modularize and govern NGS pipelines for Precision Medicine. Specifically, it provides the flexibility (i.e. the indexing) needed to support the wide variety of clinical scenarios and patient-facing governance where only part of the VCF data is fitting. Software libraries with a claim to be both domain-facing and consumer-facing have to pass the test of portability across the variety of devices that those consumers in fact adopt. That is, ideally the implementation should itself take place within the space defined by web technologies. Consequently, the isomorphic mapping function was implemented in JavaScript, and was tested in a variety of environments and devices, client and server side alike. These range from web browsers in mobile phones to the most popular micro service platform, NodeJS. The code is publicly available at https://github.com/ibl/VCFr , with a live deployment at: http://ibl.github.io/VCFr/ . jonas.almeida@stonybrookmedicine.edu. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

[Left atrial function and left atrial appendage flow velocity in hypertrophic cardiomyopathy: comparison of patients with and without paroxysmal atrial fibrillation].

PubMed

Akasaka, K; Kawashima, E; Shiokoshi, T; Ishii, Y; Hasebe, N; Kikuchi, K

1998-07-01

The involvement of left atrial (LA) appendage flow velocity in reduced left atrial function was investigated in 24 patients with hypertrophic cardiomyopathy, who retained sinus rhythm at the examination. Patients were divided into 11 with a history of paroxysmal atrial fibrillation [PAf(+)] and 13 without such history [PAf(-)]. Transthoracic echocardiography was performed to evaluate LA fractional shortening (LA%FS) and mean velocity of circumferential LA fiber shortening (LAmVcf), as contractile functions of the left atrium at the phase of active atrial contraction. Transesophageal echocardiographic Doppler examination was performed in all patients to measure the LA appendage velocity. In all patients, significant positive correlations were observed between the LA appendage velocity and LA%FS (r = 0.50, p < 0.05) or LAmVcf (r = 0.82, p < 0.001). LAmVcf and LA appendage velocity in patients with paroxysmal fibrillation were significantly lower than in those without (0.84 +/- 0.15 vs 1.28 +/- 0.37 circ/sec, 44 +/- 12 vs 65 +/- 20 cm/sec, both p < 0.01), whereas LA diameter was greater in the former compared to the latter (45 +/- 5 vs 38 +/- 5 mm, p < 0.01). LAmVcf and LA appendage velocity were low in four patients with cerebral infarction or transient cerebral ischemic attack (LAmVcf < 1.0 circ/sec, LA appendage velocity < or = 40 cm/sec). Importantly, all these patients had a history of paroxysmal fibrillation. These results indicate that there is a close relationship between LA appendage velocity and LA contractile function in patients with hypertrophic cardiomyopathy with paroxysmal atrial fibrilation, and these patients have potential risk of cerebral infarction.

Optimized distributed systems achieve significant performance improvement on sorted merging of massive VCF files

PubMed Central

Gao, Jingjing; Jin, Peng; Eng, Celeste; Burchard, Esteban G; Beaty, Terri H; Ruczinski, Ingo; Mathias, Rasika A; Barnes, Kathleen; Wang, Fusheng

2018-01-01

Abstract Background Sorted merging of genomic data is a common data operation necessary in many sequencing-based studies. It involves sorting and merging genomic data from different subjects by their genomic locations. In particular, merging a large number of variant call format (VCF) files is frequently required in large-scale whole-genome sequencing or whole-exome sequencing projects. Traditional single-machine based methods become increasingly inefficient when processing large numbers of files due to the excessive computation time and Input/Output bottleneck. Distributed systems and more recent cloud-based systems offer an attractive solution. However, carefully designed and optimized workflow patterns and execution plans (schemas) are required to take full advantage of the increased computing power while overcoming bottlenecks to achieve high performance. Findings In this study, we custom-design optimized schemas for three Apache big data platforms, Hadoop (MapReduce), HBase, and Spark, to perform sorted merging of a large number of VCF files. These schemas all adopt the divide-and-conquer strategy to split the merging job into sequential phases/stages consisting of subtasks that are conquered in an ordered, parallel, and bottleneck-free way. In two illustrating examples, we test the performance of our schemas on merging multiple VCF files into either a single TPED or a single VCF file, which are benchmarked with the traditional single/parallel multiway-merge methods, message passing interface (MPI)–based high-performance computing (HPC) implementation, and the popular VCFTools. Conclusions Our experiments suggest all three schemas either deliver a significant improvement in efficiency or render much better strong and weak scalabilities over traditional methods. Our findings provide generalized scalable schemas for performing sorted merging on genetics and genomics data using these Apache distributed systems. PMID:29762754

Treatment of mandibular angle fracture with a 2mm, 3 dimensional rectangular grid compression miniplates: A prospective clinical study.

PubMed

Mansuri, Samir; Abdulkhayum, Abdul Mujeeb; Gazal, Giath; Hussain, Mohammed Abid Zahir

2013-12-01

Surgical treatment of fracture mandible using an internal fixation has changed in the last decades to achieve the required rigidity, stability and immediate restoration of function. The aim of the study was to do a Prospective study of 10 patients to determine the efficacy of rectangular grid compression miniplates in mandibular fractures. This study was carried out using 2.0 rectangular grid compression miniplates and 8 mm multidirectional screws as a rigid internal fixation in 10 patients without post operative intermaxillary fixation (IMF). Follow up was done for period of 6 months. All fractures were healed with an absolute stability in post operative period. None of the patient complained of post operative difficulty in occlusion. Within the limits of this study, it can be concluded that rectangular grid compression miniplates was rigid, reliable and thus can be recommended for the treatment of mandibular angle fractures. How to cite this article: Mansuri S, Abdulkhayum AM, Gazal G, Hussain MA. Treatment of mandibular angle fracture with a 2mm, 3 dimensional rectangular grid compression miniplates: A prospective clinical study. J Int Oral Health 2013;5(6):93-100 .

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, J.S.; Miyamoto, Y.

The fracture behavior of graded Al{sub 2}O{sub 3}/TiC/Ni materials with a symmetric structure was investigated using single-edge notch-bend (SENB) specimens with surface compression. The fracture toughness of the graded materials was determined according to ASTM Standard E399. The results show that the effective fracture toughness increases with an increase in notch depth in the compressive stress zone, and reaches the maximum of 39.2 MPa m{sup 1/2} at the interface of compressive/tensile stress zones. Finite elements analysis reveals that the surface compression will be intensified at the notch root once the specimen is edge-notched because of the stress concentration, and themore » digress of the compressive stress intensification increases with an increase in notch depth. The dependence of the effective fracture toughness of the graded materials on the notch depth shows a behavior similar to the R-curve that is usually associated with microstructural toughening mechanisms. This toughening behavior is caused by the intensification of the compressive stress concentration with the increase of the notch depth. A theoretical analysis based on fracture mechanics verifies that the mechanical reliability of brittle ceramics can be improved effectively by tailoring and controlling the internal stresses.« less

Kyphosis

MedlinePlus

... age, and the cause and effects of the curvature. Symptoms Mild kyphosis may produce no noticeable signs ... or crushed vertebrae (compression fractures) can result in curvature of the spine. Mild compression fractures often don' ...

Experimental Study of Hybrid Fractures and the Transition From Joints to Faults

NASA Astrophysics Data System (ADS)

Ramsey, J. M.; Chester, F. M.

2003-12-01

Joints and faults are end members of a continuous spectrum of brittle fractures including the hybrid fractures, hypothesized to form under mixed compressive and tensile stress. However, unequivocal evidence for the existence of hybrid fractures has not been presented. To investigate this transition, we have conducted triaxial extension experiments on dog-bone shaped cylindrical samples of Carrara marble at room temperature, an axial extension rate of 2x10-2 mm s-1, and confining pressures between 7.5 and 170 MPa. Two parallel suites of experiments were completed, one using very weak, latex jacketing to obtain accurate failure strength, and another using copper foil jacketing to preserve fracture surfaces. The combined data set provides strong evidence for the existence of hybrid fractures on the basis of the progressive change in failure strength, fracture orientation, and fracture surface morphology from joints to faults. At the lowest confining pressures (7.5 to 60 MPa), fractures are oriented approximately parallel to the maximum principal compressive stress, form at a tensile axial stress of approximately -7.75 MPa (i.e. the uniaxial tensile strength), and display fracture surfaces characterized by many reflective grain-scale cleavage faces, consistent with jointing. At the highest confining pressures (130 to 170 MPa), fractures are oriented from 13.4 to 21.6 degrees to the maximum principal compressive stress, form under completely compressive stress states where the axial stress is between 0 and 4.3 MPa, and are characterized by short slip lineations and powdery, finely comminuted grains consistent with faulting. At intermediate confining pressures (70 to 120 MPa), fractures are oriented from 3.7 to 12.4 degrees to the maximum principal compressive stress, form under mixed stress conditions with the axial stress ranging from -10.6 to -3.0 MPa, and display both reflective cleavage faces and short slip lineations with comminuted grains, consistent with hybrid fracturing.

Microscopic Pattern of Bone Fractures as an Indicator of Blast Trauma: A Pilot Study.

PubMed

Pechníková, Marketa; Mazzarelli, Debora; Poppa, Pasquale; Gibelli, Daniele; Scossa Baggi, Emilio; Cattaneo, Cristina

2015-09-01

The assessment of fractures is a key issue in forensic anthropology; however, very few studies deal with the features of fractures due to explosion in comparison with other traumatic injuries. This study focuses on fractures resulting from blast trauma and two types of blunt force trauma (manual compression and running over), applied to corpses of pigs; 163 osteons were examined within forty fractures by the transmission light microscopy. Blast lesions showed a higher percentage of fracture lines through the Haversian canal, whereas in other types of trauma, the fractures went across the inner lamellae. Significant differences between samples hit by blast energy and those runover or manually compressed were observed (p<0.05). The frequency of pattern A is significantly higher in exploded bones than in runover and compressed. Microscopic analysis of the fracture line may provide information about the type of trauma, especially for what concerns blast trauma. © 2015 American Academy of Forensic Sciences.

Potassium Rankine cycle vapor chamber (heat pipe) radiator study

NASA Technical Reports Server (NTRS)

Gerrels, E. E.; Killen, R. E.

1971-01-01

A structurally integrated vapor chamber fin (heat pipe) radiator is defined and evaluated as a potential candidate for rejecting waste heat from the potassium Rankine cycle powerplant. Several vapor chamber fin geometries, using stainless steel construction, are evaluated and an optimum is selected. A comparison is made with an operationally equivalent conduction fin radiator. Both radiators employ NaK-78 in the primary coolant loop. In addition, the Vapor Chamber Fin (VCF) radiator utilizes sodium in the vapor chambers. Preliminary designs are developed for the conduction fin and VCF concepts. Performance tests on a single vapor chamber were conducted to verify the VCF design. A comparison shows the conduction fin radiator easier to fabricate, but heavier in weight, particularly as meteoroid protection requirements become more stringent. While the analysis was performed assuming the potassium Rankine cycle powerplant, the results are equally applicable to any system radiating heat to space in the 900 to 1400 F temperature range.

Using a new device to prevent pulmonary embolisms during pharmacomechanical thrombectomy.

PubMed

Calleja, E; Ciampi, J J; Puche, J J; Lanciego, C

2018-04-20

We have used a new device to prevent pulmonary embolism during pharmacomechanical thrombectomy in a 25-year-old postpartum woman. The Angel® catheter (BiO2 Medical Inc., Golden, CO, USA) is a temporary device that combines the functions of a vena cava filter (VCF) with those of a triple-lumen central venous catheter. Normally, a VCF is implanted to prevent pulmonary embolism during pharmacomechanical thrombectomy. However, the complications associated with VCFs increase with time, not all of the filter can always be retrieved, and there can be iatrogenic effects both during implantation and retrieval. In our experience, this new device is much simpler to deploy and to retrieve. As is shown in this case, this temporary device can be an interesting alternative to a VCF for preventing pulmonary embolisms during pharmacomechanical thrombectomy. Copyright © 2018 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.

Fatal fat embolism in isolated vertebral compression fracture

PubMed Central

Saldanha, Vilas; Balasubramanian, Manjula; Handal, John

2010-01-01

Fat embolism after long bone and pelvic fractures as well as orthopedic interventions is a well-documented phenomenon, but it is highly unusual after isolated vertebral fractures. We report a case of fatal fat embolism in a 78-year-old man after an isolated vertebral compression fracture with no related orthopedic intervention. A high index of suspicion is necessary for early diagnosis and successfully treating this unusual complication. PMID:20229119

Fatal fat embolism in isolated vertebral compression fracture.

PubMed

Lastra, Ricardo R; Saldanha, Vilas; Balasubramanian, Manjula; Handal, John

2010-07-01

Fat embolism after long bone and pelvic fractures as well as orthopedic interventions is a well-documented phenomenon, but it is highly unusual after isolated vertebral fractures. We report a case of fatal fat embolism in a 78-year-old man after an isolated vertebral compression fracture with no related orthopedic intervention. A high index of suspicion is necessary for early diagnosis and successfully treating this unusual complication.

Lumbar vertebral haemangioma causing pathological fracture, epidural haemorrhage, and cord compression: a case report and review of literature.

PubMed

Vinay, S; Khan, S K; Braybrooke, J R

2011-01-01

Vertebral haemangiomas are recognized to be one of the commonest benign tumours of the vertebral column, occurring mostly in the thoracic spine. The vast majority of these are asymptomatic. Infrequently, these can turn symptomatic and cause neurological deficit (cord compression) through any of four reported mechanisms: (1) epidural extension; (2) expansion of the involved vertebra(e) causing spinal canal stenosis; (3) spontaneous epidural haemorrhage; (4) pathological burst fracture. Thoracic haemangiomas have been reported to be more likely to produce cord compression than lumbar haemangiomas. A forty-nine year old male with acute onset spinal cord compression from a pathological fracture in a first lumbar vertebral haemangioma. An MRI delineated the haemangioma and extent of bleeding that caused the cord compression. These were confirmed during surgery and the haematoma was evacuated. The spine was instrumented from T12 to L2, and a cement vertebroplasty was performed intra-operatively. Written consent for publication was obtained from the patient. The junctional location of the first lumbar vertebra, and the structural weakness from normal bone being replaced by the haemangioma, probably caused it to fracture under axial loading. This pathological fracture caused bleeding from the vascularized bone, resulting in cord compression.

Lumbar vertebral haemangioma causing pathological fracture, epidural haemorrhage, and cord compression: a case report and review of literature

PubMed Central

Vinay, S; Khan, SK; Braybrooke, JR

2011-01-01

Context Vertebral haemangiomas are recognized to be one of the commonest benign tumours of the vertebral column, occurring mostly in the thoracic spine. The vast majority of these are asymptomatic. Infrequently, these can turn symptomatic and cause neurological deficit (cord compression) through any of four reported mechanisms: (1) epidural extension; (2) expansion of the involved vertebra(e) causing spinal canal stenosis; (3) spontaneous epidural haemorrhage; (4) pathological burst fracture. Thoracic haemangiomas have been reported to be more likely to produce cord compression than lumbar haemangiomas. Findings A forty-nine year old male with acute onset spinal cord compression from a pathological fracture in a first lumbar vertebral haemangioma. An MRI delineated the haemangioma and extent of bleeding that caused the cord compression. These were confirmed during surgery and the haematoma was evacuated. The spine was instrumented from T12 to L2, and a cement vertebroplasty was performed intra-operatively. Written consent for publication was obtained from the patient. Clinical Relevance The junctional location of the first lumbar vertebra, and the structural weakness from normal bone being replaced by the haemangioma, probably caused it to fracture under axial loading. This pathological fracture caused bleeding from the vascularized bone, resulting in cord compression. PMID:21756575

A clinical evaluation of alternative fixation techniques for medial malleolus fractures.

PubMed

Barnes, Hayley; Cannada, Lisa K; Watson, J Tracy

2014-09-01

Medial malleolus fractures have traditionally been managed using partially threaded screws and/or Kirschner wire fixation. Using these conventional techniques, a non-union rate of as high as 20% has been reported. In addition too many patients complaining of prominent hardware as a source of pain post-fixation. This study was designed to assess the outcomes of medial malleolar fixation using a headless compression screw in terms of union rate, the need for hardware removal, and pain over the hardware site. Saint Louis University and Mercy Medical Center, Level 1 Trauma Centers, St. Louis, MO. After IRB approval, we used billing records to identify all patients with ankle fractures involving the medial malleolus. Medical records and radiographs were reviewed to identify patients with medial malleolar fractures treated with headless compression screw fixation. Our inclusion criteria included follow-up until full weight bearing and a healed fracture. Follow-up clinical records and radiographs were reviewed to determine union, complication rate and perception of pain over the site of medial malleolus fixation. Sixty-four ankles were fixed via headless compression screws and 44 had adequate follow-up for additional evaluation. Seven patients had isolated medial malleolar fractures, 23 patients had bimalleolar fractures, and 14 patients had trimalleolar fractures. One patient (2%) required hardware removal due to cellulitis. One patient (2%) had a delayed union, which healed without additional intervention. Ten patients (23%) reported mild discomfort to palpation over the medial malleolus. The median follow-up was 35 weeks (range: 12-208 weeks). There were no screw removals for painful hardware and no cases of non-union. Headless compression screws provide effective compression of medial malleolus fractures and result in good clinical outcomes. The headless compression screw is a beneficial alternative to the conventional methods of medial malleolus fixation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fracture resistance of the implant-abutment connection in implants with internal hex and internal conical connections under oblique compressive loading: an in vitro study.

PubMed

Coppedê, Abílio Ricciardi; Bersani, Edmilson; de Mattos, Maria da Gloria Chiarello; Rodrigues, Renata Cristina Silveira; Sartori, Ivete Aparecida de Mattias; Ribeiro, Ricardo Faria

2009-01-01

The objective of this study was to verify if differences in the design of internal hex (IH) and internal conical (IC) connection implant systems influence fracture resistance under oblique compressive forces. Twenty implant-abutment assemblies were utilized: 10 with IH connections and 10 with IC connections. Maximum deformation force for IC implants (90.58 +/- 6.72 kgf) was statistically higher than that for IH implants (83.73 +/- 4.94 kgf) (P = .0182). Fracture force for the IH implants was 79.86 +/- 4.77 kgf. None of the IC implants fractured. The friction-locking mechanics and the solid design of the IC abutments provided greater resistance to deformation and fracture under oblique compressive loading when compared to the IH abutments.

Burst fractures of the lumbar spine in frontal crashes.

PubMed

Kaufman, Robert P; Ching, Randal P; Willis, Margaret M; Mack, Christopher D; Gross, Joel A; Bulger, Eileen M

2013-10-01

In the United States, major compression and burst type fractures (>20% height loss) of the lumbar spine occur as a result of motor vehicle crashes, despite the improvements in restraint technologies. Lumbar burst fractures typically require an axial compressive load and have been known to occur during a non-horizontal crash event that involve high vertical components of loading. Recently these fracture patterns have also been observed in pure horizontal frontal crashes. This study sought to examine the contributing factors that would induce an axial compressive force to the lumbar spine in frontal motor vehicle crashes. We searched the National Automotive Sampling System (NASS, 1993-2011) and Crash Injury Research and Engineering Network (CIREN, 1996-2012) databases to identify all patients with major compression lumbar spine (MCLS) fractures and then specifically examined those involved in frontal crashes. National trends were assessed based on weighted NASS estimates. Using a case-control study design, NASS and CIREN cases were utilized and a conditional logistic regression was performed to assess driver and vehicle characteristics. CIREN case studies and biomechanical data were used to illustrate the kinematics and define the mechanism of injury. During the study period 132 NASS cases involved major compression lumbar spine fractures for all crash directions. Nationally weighted, this accounted for 800 cases annually with 44% of these in horizontal frontal crashes. The proportion of frontal crashes resulting in MCLS fractures was 2.5 times greater in late model vehicles (since 2000) as compared to 1990s models. Belted occupants in frontal crashes had a 5 times greater odds of a MCLS fracture than those not belted, and an increase in age also greatly increased the odds. In CIREN, 19 cases were isolated as horizontal frontal crashes and 12 of these involved a major compression lumbar burst fracture primarily at L1. All were belted and almost all occurred in late model vehicles with belt pretensioners and buckets seats. Major compression burst fractures of the lumbar spine in frontal crashes were induced via a dynamic axial force transmitted to the pelvis/buttocks into the seat cushion/pan involving belted occupants in late model vehicles with increasing age as a significant factor. Copyright © 2013 Elsevier Ltd. All rights reserved.

Dynamic Stabilization of Simple Fractures With Active Plates Delivers Stronger Healing Than Conventional Compression Plating

PubMed Central

Tsai, Stanley; Bliven, Emily K.; von Rechenberg, Brigitte; Kindt, Philipp; Augat, Peter; Henschel, Julia; Fitzpatrick, Daniel C.; Madey, Steven M.

2017-01-01

Objectives: Active plates dynamize a fracture by elastic suspension of screw holes within the plate. We hypothesized that dynamic stabilization with active plates delivers stronger healing relative to standard compression plating. Methods: Twelve sheep were randomized to receive either a standard compression plate (CP) or an active plate (ACTIVE) for stabilization of an anatomically reduced tibial osteotomy. In the CP group, absolute stabilization was pursued by interfragmentary compression with 6 cortical screws. In the ACTIVE group, dynamic stabilization after bony apposition was achieved with 6 elastically suspended locking screws. Fracture healing was analyzed weekly on radiographs. After sacrifice 9 weeks postsurgery, the torsional strength of healed tibiae and contralateral tibiae was measured. Finally, computed tomography was used to assess fracture patterns and healing modes. Results: Healing in both groups included periosteal callus formation. ACTIVE specimens had almost 6 times more callus area by week 9 (P < 0.001) than CP specimens. ACTIVE specimens recovered on average 64% of their native strength by week 9, and were over twice as strong as CP specimens, which recovered 24% of their native strength (P = 0.008). Microcomputed tomography demonstrated that compression plating induced a combination of primary bone healing and gap healing. Active plating consistently stimulated biological bone healing by periosteal callus formation. Conclusions: Compared with compression plating, dynamic stabilization of simple fractures with active plates delivers significantly stronger healing. PMID:27861456

Unhole and open hole compressive behaviours of hybrid Kevlar/glass fibre reinforced silica nanocomposites

NASA Astrophysics Data System (ADS)

Shaari, Norazean; Jumahat, Aidah

2018-06-01

The paper presents the effects of hybridization and silica nanoparticles on unhole and open hole compressive behaviours of woven Kevlar/glass fibre hybrid composite laminates. Residual compressive strength and stiffness were determined from an open hole compression (OHC) test conducted according to ASTM D6484-09, whereas the fractured surface behaviour was observed under scanning electron microscope (SEM). Silica nanoparticles were mixed into the epoxy resins using vacuum mechanical stirrer. Then, composite laminates were prepared using vacuum bagging method. Three different silica nanoparticles contents (5 wt%, 13 wt% and 25 wt%) were incorporated into the resin system with three different hybrid system (20:80, 50:50 and 80:20 of Kevlar fibres to glass fibres ratio). Results showed that the lowest compressive strength was observed in Kevlar fibre reinforced polymer. Therefore, hybridization of glass fibres with Kevlar fibres reduced the compressive strength of hybrid composites. However, the incorporation of silica nanoparticles into the epoxy resins improved the compressive properties of the hybrid composites. From the observation of the fractured surface, different fracture behaviours were observed in both Kevlar fibre and glass fibre composites. Fibre barrelling and crimping was observed in Kevlar fibres while glass fibres showed a fibre fracture with serrated and rough surfaces.

Rock deformation models and fluid leak-off in hydraulic fracturing

NASA Astrophysics Data System (ADS)

Yarushina, Viktoriya M.; Bercovici, David; Oristaglio, Michael L.

2013-09-01

Fluid loss into reservoir rocks during hydraulic fracturing is modelled via a poro-elastoplastic pressure diffusion equation in which the total compressibility is a sum of fluid, rock and pore space compressibilities. Inclusion of pore compressibility and porosity-dependent permeability in the model leads to a strong pressure dependence of leak-off (i.e. drainage rate). Dilation of the matrix due to fluid invasion causes higher rates of fluid leak-off. The present model is appropriate for naturally fractured and tight gas reservoirs as well as for soft and poorly consolidated formations whose mechanical behaviour departs from simple elastic laws. Enhancement of the leak-off coefficient by dilation, predicted by the new model, may help explain the low percentage recovery of fracturing fluid (usually between 5 and 50 per cent) in shale gas stimulation by hydraulic fracturing.

Stress analysis of implant-bone fixation at different fracture angle

NASA Astrophysics Data System (ADS)

Izzawati, B.; Daud, R.; Afendi, M.; Majid, MS Abdul; Zain, N. A. M.; Bajuri, Y.

2017-10-01

Internal fixation is a mechanism purposed to maintain and protect the reduction of a fracture. Understanding of the fixation stability is necessary to determine parameters influence the mechanical stability and the risk of implant failure. A static structural analysis on a bone fracture fixation was developed to simulate and analyse the biomechanics of a diaphysis shaft fracture with a compression plate and conventional screws. This study aims to determine a critical area of the implant to be fractured based on different implant material and angle of fracture (i.e. 0°, 30° and 45°). Several factors were shown to influence stability to implant after surgical. The stainless steel, (S. S) and Titanium, (Ti) screws experienced the highest stress at 30° fracture angle. The fracture angle had a most significant effect on the conventional screw as compared to the compression plate. The stress was significantly higher in S.S material as compared to Ti material, with concentrated on the 4th screw for all range of fracture angle. It was also noted that the screws closest to the intense concentration stress areas on the compression plate experienced increasing amounts of stress. The highest was observed at the screw thread-head junction.

Altered disc pressure profile after an osteoporotic vertebral fracture is a risk factor for adjacent vertebral body fracture

PubMed Central

Tzermiadianos, Michael N.; Renner, Susan M.; Phillips, Frank M.; Hadjipavlou, Alexander G.; Zindrick, Michael R.; Havey, Robert M.; Voronov, Michael

2008-01-01

This study investigated the effect of endplate deformity after an osteoporotic vertebral fracture in increasing the risk for adjacent vertebral fractures. Eight human lower thoracic or thoracolumbar specimens, each consisting of five vertebrae were used. To selectively fracture one of the endplates of the middle VB of each specimen a void was created under the target endplate and the specimen was flexed and compressed until failure. The fractured vertebra was subjected to spinal extension under 150 N preload that restored the anterior wall height and vertebral kyphosis, while the fractured endplate remained significantly depressed. The VB was filled with cement to stabilize the fracture, after complete evacuation of its trabecular content to ensure similar cement distribution under both the endplates. Specimens were tested in flexion-extension under 400 N preload while pressure in the discs and strain at the anterior wall of the adjacent vertebrae were recorded. Disc pressure in the intact specimens increased during flexion by 26 ± 14%. After cementation, disc pressure increased during flexion by 15 ± 11% in the discs with un-fractured endplates, while decreased by 19 ± 26.7% in the discs with the fractured endplates. During flexion, the compressive strain at the anterior wall of the vertebra next to the fractured endplate increased by 94 ± 23% compared to intact status (p < 0.05), while it did not significantly change at the vertebra next to the un-fractured endplate (18.2 ± 7.1%, p > 0.05). Subsequent flexion with compression to failure resulted in adjacent fracture close to the fractured endplate in six specimens and in a non-adjacent fracture in one specimen, while one specimen had no adjacent fractures. Depression of the fractured endplate alters the pressure profile of the damaged disc resulting in increased compressive loading of the anterior wall of adjacent vertebra that predisposes it to wedge fracture. This data suggests that correction of endplate deformity may play a role in reducing the risk of adjacent fractures. PMID:18795344

Failure Mechanisms of Brittle Rocks under Uniaxial Compression

NASA Astrophysics Data System (ADS)

Liu, Taoying; Cao, Ping

2017-09-01

The behaviour of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities or fractures within the mass. The compression test on rock-like specimens with two prefabricated transfixion fissures, made by pulling out the embedded metal inserts in the pre-cured period was carried out on the servo control uniaxial loading tester. The influence of the geometry of pre-existing cracks on the cracking processes was analysed with reference to the experimental observation of crack initiation and propagation from pre-existing flaws. Based on the rock fracture mechanics and the stress-strain curves, the evolution failure mechanism of the fissure body was also analyzed on the basis of exploring the law of the compression-shear crack initiation, wing crack growth and rock bridge connection. Meanwhile, damage fracture mechanical models of a compression-shear rock mass are established when the rock bridge axial transfixion failure, tension-shear combined failure, or wing crack shear connection failure occurs on the specimen under axial compression. This research was of significance in studying the failure mechanism of fractured rock mass.

Object-based Mapping of the Circumpolar Taiga-Tundra Ecotone with MODIS Tree Cover

NASA Technical Reports Server (NTRS)

Ransom, Kenneth J.; Montesano, Paul M.; Nelson, Ross F.

2011-01-01

The circumpolar taiga-tundra ecotone was delineated using an image segmentation based mapping approach with multi-annual MODIS Vegetation Continuous Fields (VCF) tree cover data. Circumpolar tree canopy cover (TCC) throughout the ecotone was derived by averaging MODIS VCF data from 2000 - 2005 and adjusting the averaged values using linear equations relating MODIS TCC to Quickbird-derived tree cover estimates. The adjustment helped mitigate VCF's overestimation of tree cover in lightly forested regions. An image segmentation grouped pixels representing similar tree cover into polygonal features (objects) that form the map of the transition zone. Eachfeature represents an area much larger than the 500m MODIS pixel to characterize thepatterns of sparse forest patches on a regional scale. Comparisons of the adjusted average tree cover data were made with (1) two existing tree line definitions aggregated for each 1deg longitudinal interval in North America and Eurasia and (2) Landsat-derived Canadianproportion of forest cover for Canada. The adjusted TCC from MODIS VCF shows, on average, greater than 12% TCC for all but one regional zone at the intersection with independently delineated tree lines. Adjusted values track closely with Canadian proportion of forest cover data in areas of low tree cover. Those polygons near the boreal/tundra interface with either (1) mean adjusted TCC values between 5-20% , or (2) mean adjusted TCC values <5% but with a standard deviation > 5% were used to identify the ecotone.

[Surgical treatment of tibial nonunion after wounding by high velocity missile and external fixators: a case report].

PubMed

Golubović, Ivan; Vukašinović, Zoran; Stojiljković, Predrag; Golubović, Zoran; Stojiljković, Danilo; Radovanović, Zoran; Ilić, Nenad; Najman, Stevo; Višnjić, Aleksandar; Arsić, Stojanka

2012-01-01

The missiles of modern firearms can cause severe fractures of the extremity. High velocity missile fractures of the tibia are characterized by massive tissue destruction and primary contamination with polymorphic bacteria. Treatment of these fractures is often complicated by delayed healing, poor position healing, nonhealing and bone tissue infection. We present the management of tibial nonunion after wounding by high velocity missile and primary treatment by external fixation in a 25-year-old patient. The patient was primarily treated with external fixation and reconstructive operations of the soft tissue without union of the fracture. Seven months after injury we placed a compression-distraction external fixator type Mitkovic and started with compression and distraction in the fracture focus after osteotomy of the fibula and autospongioplasty. We recorded satisfactory fracture healing and good functional outcome. Contamination and devitalization of the soft-tissue envelope increase the risk of infection and nonunion in fractures after wounding by high velocity missile. The use of the compression-distraction external fixator type Mitkovic may be an effective method in nonunions of the tibia after this kind of injury.

Compressive rib fracture: peri-mortem and post-mortem trauma patterns in a pig model.

PubMed

Kieser, Jules A; Weller, Sarah; Swain, Michael V; Neil Waddell, J; Das, Raj

2013-07-01

Despite numerous studies on high impact fractures of ribs, little is known about compressive rib injuries. We studied rib fractures from a biomechanical and morphological perspective using 15, 5th ribs of domestic pigs Sus scrofa, divided into two groups, desiccated (representing post-mortem trauma) and fresh ribs with intact periosteum (representing peri-mortem trauma). Ribs were axially compressed and subjected to four-point bending in an Instron 3339 fitted with custom jigs. Morphoscopic analysis of resultant fractures consisted of standard optical methods, micro-CT (μCT) and scanning electron microscopy (SEM). During axial compression, fresh ribs had slightly higher strength because of energy absorption capabilities of their soft and fluidic components. In flexure tests, dry ribs showed typical elastic-brittle behaviour with long linear load-extension curves, followed by relatively short non-linear elastic (hyperelastic) behaviour and brittle fracture. Fresh ribs showed initial linear-elastic behaviour, followed by strain softening, visco-plastic responses. During the course of loading, dry bone showed minimal observable damage prior to the onset of unstable fracture. In contrast, fresh bone showed buckling-like damage features on the compressive surface and cracking parallel to the axis of the bone. Morphologically, all dry ribs fractured precipitously, whereas all but one of the fresh ribs showed incomplete fracture. The mode of fracture, however, was remarkably similar for both groups, with butterfly fractures predominating (7/15, 46.6% dry and wet). Our study highlights the fact that under controlled loading, despite seemingly similar butterfly fracture morphology, fresh ribs (representing perimortem trauma) show a non-catastrophic response. While extensive strain softening observed for the fresh bone does show some additional micro-cracking damage, it appears that the periosteum may play a key role in imparting the observed pseudo-ductility to the ribs. The presence of fibrous pull-out and grooving of the outer tensile surface associated with periosteal stretching suggests that the periosteum under tension is able to sustain very high strain and bridge the mouth of the extending butterfly crack, thereby contributing to the observed strain-softening behaviour. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Foam relaxation in fractures and narrow channels

NASA Astrophysics Data System (ADS)

Lai, Ching-Yao; Rallabandi, Bhargav; Perazzo, Antonio; Stone, Howard A.

2017-11-01

Various applications, from foam manufacturing to hydraulic fracturing with foams, involve pressure-driven flow of foams in narrow channels. We report a combined experimental and theoretical study of this problem accounting for the compressible nature of the foam. In particular, in our experiments the foam is initially compressed in one channel and then upon flow into a second channel the compressed foam relaxes as it moves. A plug flow is observed in the tube and the pressure at the entrance of the tube is higher than the exit. We measure the volume collected at the exit of the tube, V, as a function of injection flow rate, tube length and diameter. Two scaling behaviors for V as a function of time are observed depending on whether foam compression is important or not. Our work may relate to foam fracturing, which saves water usage in hydraulic fracturing, more efficient enhanced oil recovery via foam injection, and various materials manufacturing processes involving pressure-driven flow foams.

The fracture characteristic of three collinear cracks under true triaxial compression.

PubMed

Liu, Jianjun; Zhu, Zheming; Wang, Bo

2014-01-01

The mechanical behavior of multicracks under compression has become a very important project in the field of fracture mechanics and rock mechanics. In this paper, experimental and numerical studies on the fracture property of three collinear cracks under compression were implemented. The specimens were a square concrete plate, and the cracks were made by a very thin film. The tests were conducted by using true triaxial loading device. In the numerical study, the Abaqus code was employed. The effect of crack orientation and the confining stress on cracked specimen compressive strength were investigated. The results show that the critical stresses of cracked specimens change with crack inclination angles, and, as the angle is 45°, the critical stress is the lowest; the critical stresses increase with the confining stresses.

The Fracture Characteristic of Three Collinear Cracks under True Triaxial Compression

PubMed Central

Liu, Jianjun; Zhu, Zheming; Wang, Bo

2014-01-01

The mechanical behavior of multicracks under compression has become a very important project in the field of fracture mechanics and rock mechanics. In this paper, experimental and numerical studies on the fracture property of three collinear cracks under compression were implemented. The specimens were a square concrete plate, and the cracks were made by a very thin film. The tests were conducted by using true triaxial loading device. In the numerical study, the Abaqus code was employed. The effect of crack orientation and the confining stress on cracked specimen compressive strength were investigated. The results show that the critical stresses of cracked specimens change with crack inclination angles, and, as the angle is 45°, the critical stress is the lowest; the critical stresses increase with the confining stresses. PMID:24790569

Chromosome 22q11.2 deletion in a boy with Opitz (G/BBB) syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fryburg, J.S.; Lin, K.Y.; Golden, W.L.

This report is on a 14-month-old boy with manifestations of Opitz (G/BBB) syndrome in whom a 22q11.2 deletion was found. Deletion analysis was requested because of some findings in this patient reminiscent of velocardiofacial (VCF) syndrome. The extent of aspiration and of respiratory symptoms in this child is not usually seen in VCF syndrome. Opitz syndrome maps to at least two loci, one on Xp, the other on 22q11.2. 12 refs., 2 figs.

LagLoc - a new surgical technique for locking plate systems.

PubMed

Triana, Miguel; Gueorguiev, Boyko; Sommer, Christoph; Stoffel, Karl; Agarwal, Yash; Zderic, Ivan; Helfen, Tobias; Krieg, James C; Krause, Fabian; Knobe, Matthias; Richards, R Geoff; Lenz, Mark

2018-06-19

Treatment of oblique and spiral fractures remains challenging. The aim of this study was to introduce and investigate the new LagLoc technique for locked plating with generation of interfragmentary compression, combining the advantages of lag-screw and locking-head-screw techniques. Oblique fracture was simulated in artificial diaphyseal bones, assigned to three groups for plating with a 7-hole locking compression plate. Group I was plated with three locking screws in holes 1, 4 and 7. The central screw crossed the fracture line. In group II the central hole was occupied with a lag screw perpendicular to fracture line. Group III was instrumented applying the LagLoc technique as follows. Hole 4 was predrilled perpendicularly to the plate, followed by overdrilling of the near cortex and insertion of a locking screw whose head was covered by a holding sleeve to prevent temporarily the locking in the plate hole and generate interfragmentary compression. Subsequently, the screw head was released and locked in the plate hole. Holes 1 and 7 were occupied with locking screws. Interfragmentary compression in the fracture gap was measured using pressure sensors. All screws in the three groups were tightened with 4Nm torque. Interfragmentary compression in group I (167 ± 25N) was significantly lower in comparison to groups II (431 ± 21N) and III (379 ± 59N), p≤0.005. The difference in compression between groups II and III remained not significant (p = 0.999). The new LagLoc technique offers an alternative tool to generate interfragmentary compression with the application of locking plates by combining the biomechanical advantages of lag screw and locking screw fixations. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Biomechanics of the Proximal Radius Following Drilling of the Bicipital Tuberosity to Mimic Cortical Button Distal Biceps Repair Technique.

PubMed

Oak, Nikhil R; Lien, John R; Brunfeldt, Alexander; Lawton, Jeffrey N

2018-05-01

A fracture through the proximal radius is a theoretical concern after cortical button distal biceps fixation in an active patient. The permanent, nonossified cortical defect and medullary tunnel is at risk during a fall eliciting rotational and compressive forces. We hypothesized that during simulated torsion and compression, in comparison with unaltered specimens, the cortical button distal biceps repair model would have decreased torsional and compressive strength and would fracture in the vicinity of the bicipital tuberosity bone tunnel. Sixteen fourth-generation composite radius Sawbones models were used in this controlled laboratory study. A bone tunnel was created through the bicipital tuberosity to mimic the exact bone tunnel, 8 mm near cortex and 3.2 mm far cortex, made for the BicepsButton distal biceps tendon repair. The radius was then prepared and mounted on either a torsional or compression testing device and compared with undrilled control specimens. Compression tests resulted in average failure loads of 9015.2 N in controls versus 8253.25 N in drilled specimens ( P = .074). Torsional testing resulted in an average failure torque of 27.3 Nm in controls and 19.3 Nm in drilled specimens ( P = .024). Average fracture angle was 35.1° in controls versus 21.1° in drilled. Gross fracture patterns were similar in compression testing; however, in torsional testing all fractures occurred through the bone tunnel in the drilled group. There are weaknesses in the vicinity of the bone tunnel in the proximal radius during biomechanical stress testing which may not be clinically relevant in nature. In cortical button fixation, distal biceps repairs creates a permanent, nonossified cortical defect with tendon interposed in the bone tunnel, which can alter the biomechanical properties of the proximal radius during compressive and torsional loading.

Fabric controls on the brittle failure of folded gneiss and schist

NASA Astrophysics Data System (ADS)

Agliardi, Federico; Zanchetta, Stefano; Crosta, Giovanni B.

2014-12-01

We experimentally studied the brittle failure behaviour of folded gneiss and schist. Rock fabric and petrography were characterised by meso-structural analyses, optical microscopy, X-ray diffraction, and SEM imaging. Uniaxial compression, triaxial compression and indirect tension laboratory tests were performed to characterise their strength and stress-strain behaviour. Fracture patterns generated in compression were resolved in 3D through X-ray computed tomography at different resolutions (30 to 625 μm). Uniaxial compression tests revealed relatively low and scattered values of unconfined compressive strength (UCS) and Young's modulus, with no obvious relationships with the orientation of foliation. Samples systematically failed in four brittle modes, involving different combinations of shear fractures along foliation or parallel to fold axial planes, or the development of cm-scale shear zones. Fracture quantification and microstructural analysis show that different failure modes occur depending on the mutual geometrical arrangement and degree of involvement of two distinct physical anisotropies, i.e. the foliation and the fold axial planes. The Axial Plane Anisotropy (APA) is related to micro-scale grain size reduction and shape preferred orientation within quartz-rich domains, and to mechanical rotation or initial crenulation cleavage within phyllosilicate-rich domains at fold hinge zones. In quartz-rich rocks (gneiss), fracture propagation through quartz aggregates forming the APA corresponds to higher fracture energy and strength than found for fracture through phyllosilicate-rich domains. This results in a strong dependence of strength on the failure mode. Conversely, in phyllosilicate-rich rocks (schist), all the failure modes are dominated by the strength of phyllosilicates, resulting in a sharp reduction of strength anisotropy.

Effect of overglazed and polished surface finishes on the compressive fracture strength of machinable ceramic materials.

PubMed

Asai, Tetsuya; Kazama, Ryunosuke; Fukushima, Masayoshi; Okiji, Takashi

2010-11-01

Controversy prevails over the effect of overglazing on the fracture strength of ceramic materials. Therefore, the effects of different surface finishes on the compressive fracture strength of machinable ceramic materials were investigated in this study. Plates prepared from four commercial brands of ceramic materials were either surface-polished or overglazed (n=10 per ceramic material for each surface finish), and bonded to flat surfaces of human dentin using a resin cement. Loads at failure were determined and statistically analyzed using two-way ANOVA and Bonferroni test. Although no statistical differences in load value were detected between polished and overglazed groups (p>0.05), the fracture load of Vita Mark II was significantly lower than those of ProCAD and IPS Empress CAD, whereas that of IPS e.max CAD was significantly higher than the latter two ceramic materials (p<0.05). It was concluded that overglazed and polished surfaces produced similar compressive fracture strengths irrespective of the machinable ceramic material tested, and that fracture strength was material-dependent.

Molecular characterization of a strong candidate region for schizophrenia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karayiorgou, M.; Housman, D.E.; Morrow, B.

Two lines of evidence point to a region on chromosome 22 as potentially involved in the etiology of schizophrenia: First, our own linkage data and second, observations that a greater than expected number of cases with the VCF (velo-cardio-facial) syndrome, a developmental syndrome due to microdeletions of the same genetic region, develop psychotic illness during adolescence. On the molecular genetic level, we are testing the hypothesis that the partial phenotypic overlap between schizophrenia and VCF may be due to overlapping genetic abnormalities. To that end, we have generated somatic cell hybrids from an initial group of nine VCF patients overmore » the age of 15 who underwent psychiatric evaluation. Three were assigned a DSM-III-R diagnosis of schizophrenia. Several hybrid cell lines were generated from each patient carrying either the deleted chromosome, or the intact chromosome, or both. We have analyzed these hybrids and the extent of their chromosome 22 deletions with 41 markers so far (21 polymorphic microsatellite markers and 20 STSs). One of these markers is COMT (catechol-O-methyltransferase) that could be considered a candidate for schizophrenia. We are searching for potential molecular genetic differences between the subgroup of VCF patients that do develop schizophrenia and the subgroup that do not. Our initial efforts concentrate on the possibility of correlation between the extent of the deletion and the schizophrenic phenotype. Results from our analysis so far will be presented. Our goal is to narrow and define more accurately the region potentially involved in the etiology of schizophrenia and successfully identify any gene(s) that may play a role.« less

Lateral compression open cap splint with circummandibular wiring for management of pediatric mandibular fractures: a retrospective audit of 10 cases.

PubMed

Bhola, Nitin; Jadhav, Anendd; Borle, Rajiv; Khemka, Gaurav; Adwani, Nitin; Bhattad, Mayur

2014-03-01

Mandibular fractures are relatively less frequent in children when compared to adults. Pediatric patients present a unique challenge to maxillofacial surgeons in terms of their treatment planning and in their functional needs. We currently describe our experience with lateral compression open cap splint with circummandibular wiring as a treatment modality which involves fewer risks in treating pediatric symphysis/parasymphysis/body mandibular fractures. A retrospective analysis of pediatric patients with mandibular symphysis/parasymphysis/body fractures operated from January 2007 to January 2012 was performed. Clinical photographs and orthopantomogram assessment at the time of presentation, after treatment, and at 6 months postoperatively were evaluated. All the 10 patients were followed up until the period of 6 months, and none of them had any major complications. Postoperatively, there was satisfactory healing and union of fracture fragments in all the patients. Only one patient developed infection at submental region. The 6-month follow-up showed good occlusion, without interference in teeth eruption and no signs of temporomandibular joint problems. Lateral compression open cap splints for treatment of pediatric mandibular symphysis/parasymphysis/body fractures are reliable treatment modalities with regard to occlusion-guided fracture reduction.

Treating osteoporotic vertebral compression fractures with intraosseous vacuum phenomena using high-viscosity bone cement via bilateral percutaneous vertebroplasty

PubMed Central

Guo, Dan; Cai, Jun; Zhang, Shengfei; Zhang, Liang; Feng, Xinmin

2017-01-01

Abstract Osteoporotic vertebral compression fractures with intraosseous vacuum phenomena could cause persistent back pains in patients, even after receiving conservative treatment. The aim of this study was to evaluate the efficacy of using high-viscosity bone cement via bilateral percutaneous vertebroplasty in treating patients who have osteoporotic vertebral compression fractures with intraosseous vacuum phenomena. Twenty osteoporotic vertebral compression fracture patients with intraosseous vacuum phenomena, who received at least 2 months of conservative treatment, were further treated by injecting high-viscosity bone cement via bilateral percutaneous vertebroplasty due to failure of conservative treatment. Treatment efficacy was evaluated by determining the anterior vertebral compression rates, visual analog scale (VAS) scores, and Oswestry disability index (ODI) scores at 1 day before the operation, on the first day of postoperation, at 1-month postoperation, and at 1-year postoperation. Three of 20 patients had asymptomatic bone cement leakage when treated via percutaneous vertebroplasty; however, no serious complications related to these treatments were observed during the 1-year follow-up period. A statistically significant improvement on the anterior vertebral compression rates, VAS scores, and ODI scores were achieved after percutaneous vertebroplasty. However, differences in the anterior vertebral compression rate, VAS score, and ODI score in the different time points during the 1-year follow-up period was not statistically significant (P > 0.05). Within the limitations of this study, the injection of high-viscosity bone cement via bilateral percutaneous vertebroplasty for patients who have osteoporotic vertebral compression fractures with intraosseous vacuum phenomena significantly relieved their back pains and improved their daily life activities shortly after the operation, thereby improving their life quality. In this study, the use of high-viscosity bone cement reduced the leakage rate and contributed to their successful treatment, as observed in patients during the 1-year follow-up period. PMID:28383423

A comparison between rib fracture patterns in peri- and post-mortem compressive injury in a piglet model.

PubMed

Bradley, Amanda L; Swain, Michael V; Neil Waddell, J; Das, Raj; Athens, Josie; Kieser, Jules A

2014-05-01

Forensic biomechanics is increasingly being used to explain how observed injuries occur. We studied infant rib fractures from a biomechanical and morphological perspective using a porcine model. We used 24, 6th ribs of one day old domestic pigs Sus scrofa, divided into three groups, desiccated (representing post-mortem trauma), fresh ribs with intact periosteum (representing peri-mortem trauma) and those stored at -20°C. Two experiments were designed to study their biomechanical behaviour fracture morphology: ribs were axially compressed and subjected to four-point bending in an Instron 3339 fitted with custom jigs. Morphoscopic analysis of resultant fractures consisted of standard optical methods, micro-CT (μCT) and Scanning Electron Microscopy (SEM). During axial compression fresh ribs did not fracture because of energy absorption capabilities of their soft and fluidic components. In flexure tests, dry ribs showed typical elastic-brittle behaviour with long linear load-extension curves, followed by short non-linear elastic (hyperelastic) behaviour and brittle fracture. Fresh ribs showed initial linear-elastic behaviour, followed by strain softening and visco-plastic responses. During the course of loading, dry bone showed minimal observable damage prior to the onset of unstable fracture. Frozen then thawed bone showed similar patterns to fresh bone. Morphologically, fresh ribs showed extensive periosteal damage to the tensile surface with areas of collagen fibre pull-out along the tensile surface. While all dry ribs fractured precipitously, with associated fibre pull-out, the latter feature was absent in thawed ribs. Our study highlights the fact that under controlled loading, fresh piglet ribs (representing perimortem trauma) did not fracture through bone, but was associated with periosteal tearing. These results suggest firstly, that complete lateral rib fracture in infants may in fact not result from pure compression as has been previously assumed; and secondly, that freezing of bone during storage may affect its fracture behaviour. Copyright © 2013 Elsevier Ltd. All rights reserved.

Remote sensing change detection methods to track deforestation and growth in threatened rainforests in Madre de Dios, Peru

USGS Publications Warehouse

Shermeyer, Jacob S.; Haack, Barry N.

2015-01-01

Two forestry-change detection methods are described, compared, and contrasted for estimating deforestation and growth in threatened forests in southern Peru from 2000 to 2010. The methods used in this study rely on freely available data, including atmospherically corrected Landsat 5 Thematic Mapper and Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation continuous fields (VCF). The two methods include a conventional supervised signature extraction method and a unique self-calibrating method called MODIS VCF guided forest/nonforest (FNF) masking. The process chain for each of these methods includes a threshold classification of MODIS VCF, training data or signature extraction, signature evaluation, k-nearest neighbor classification, analyst-guided reclassification, and postclassification image differencing to generate forest change maps. Comparisons of all methods were based on an accuracy assessment using 500 validation pixels. Results of this accuracy assessment indicate that FNF masking had a 5% higher overall accuracy and was superior to conventional supervised classification when estimating forest change. Both methods succeeded in classifying persistently forested and nonforested areas, and both had limitations when classifying forest change.

Fracture in compression of brittle solids

NASA Technical Reports Server (NTRS)

1983-01-01

The fracture of brittle solids in monotonic compression is reviewed from both the mechanistic and phenomenological points of view. The fundamental theoretical developments based on the extension of pre-existing cracks in general multiaxial stress fields are recognized as explaining extrinsic behavior where a single crack is responsible for the final failure. In contrast, shear faulting in compression is recognized to be the result of an evolutionary localization process involving en echelon action of cracks and is termed intrinsic.

Polydimethylsiloxane pressure sensors for force analysis in tension band wiring of the olecranon.

PubMed

Zens, Martin; Goldschmidtboeing, Frank; Wagner, Ferdinand; Reising, Kilian; Südkamp, Norbert P; Woias, Peter

2016-11-14

Several different surgical techniques are used in the treatment of olecranon fractures. Tension band wiring is one of the most preferred options by surgeons worldwide. The concept of this technique is to transform a tensile force into a compression force that adjoins two surfaces of a fractured bone. Currently, little is known about the resulting compression force within a fracture. Sensor devices are needed that directly transduce the compression force into a measurement quality. This allows the comparison of different surgical techniques. Ideally the sensor devices ought to be placed in the gap between the fractured segments. The design, development and characterization of miniaturized pressure sensors fabricated entirely from polydimethylsiloxane (PDMS) for a placement within a fracture is presented. The pressure sensors presented in this work are tested, calibrated and used in an experimental in vitro study. The pressure sensors are highly sensitive with an accuracy of approximately 3 kPa. A flexible fabrication process for various possible applications is described. The first in vitro study shows that using a single-twist or double-twist technique in tension band wiring of the olecranon has no significant effect on the resulting compression forces. The in vitro study shows the feasibility of the proposed measurement technique and the results of a first exemplary study.

Biomechanical properties of a structurally optimized carbon-fibre/epoxy intramedullary nail for femoral shaft fracture fixation.

PubMed

Samiezadeh, Saeid; Fawaz, Zouheir; Bougherara, Habiba

2016-03-01

Intramedullary nails are the golden treatment option for diaphyseal fractures. However, their high stiffness can shield the surrounding bone from the natural physiologic load resulting in subsequent bone loss. Their stiff structure can also delay union by reducing compressive loads at the fracture site, thereby inhibiting secondary bone healing. Composite intramedullary nails have recently been introduced to address these drawbacks. The purpose of this study is to evaluate the mechanical properties of a previously developed composite IM nail made of carbon-fibre/epoxy whose structure was optimized based on fracture healing requirements using the selective stress shielding approach. Following manufacturing, the cross-section of the composite nail was examined under an optical microscope to find the porosity of the structure. Mechanical properties of the proposed composite intramedullary nail were determined using standard tension, compression, bending, and torsion tests. The failed specimens were then examined to obtain the modes of failure. The material showed high strength in tension (403.9±7.8MPa), compression (316.9±10.9MPa), bending (405.3±8.1MPa), and torsion (328.5±7.3MPa). Comparing the flexural modulus (41.1±0.9GPa) with the compressive modulus (10.0±0.2GPa) yielded that the material was significantly more flexible in compression than in bending. This customized flexibility along with the high torsional stiffness of the nail (70.7±2.0Nm(2)) has made it ideal as a fracture fixation device since this unique structure can stabilize the fracture while allowing for compression of fracture ends. Negligible moisture absorption (~0.5%) and low porosity of the laminate structure (< 3%) are other advantages of the proposed structure. The findings suggested that the carbon-fibre/epoxy intramedullary nail is flexible axially while being relatively rigid in bending and torsion and is strong enough in all types of physiologic loading, making it a potential candidate for use as an alternative to the conventional titanium-alloy intramedullary nails. Copyright © 2015 Elsevier Ltd. All rights reserved.

Prone position in balloon kyphoplasty leads to no secondary vertebral compression fractures in osteoporotic spine – a MRI study

PubMed Central

Spalteholz, Matthias; Strasser, Evald; Hantel, Torsten; Gahr, Ralf Herbert

2014-01-01

Purpose: Vertebral compression fractures are the most common fractures in the elderly. Long lasting pain and deformity is responsible for consecutive impairment with markedly reduced life quality, increased morbidity and mortality. The beneficial effects of balloon kyphoplasty are verified in many studies. Subsequent fracture risk is not finally clarified, cement related risks and deformity related risks are discussed. There is less knowledge about the risk of bone marrow edema and new fractures during balloon kyphoplasty procedure. The goal of this study is to examine, if prone position during kyphoplasty is an independent risk factor for new fractures in the osteoporotic spine. Methods: Consecutive MRI study of 20 patients with fresh, non-traumatic thoracolumbar vertebral compression fractures and balloon kyphoplasty treatment. MRI Scans of the thoracolumbar spine were obtained after surgery, before patients have been mobilized. Specific MRI changes like new bone marrow edema, signal intensity changes in adjacent and remote segments and new fractures were assessed by specialized neuro-radiologist. Results: 20 MR images were examined within 48 hours after balloon kyphoplasty procedure. 85% did not show bone marrow edema extent changes after kyphoplasty. We found minor increase of bone marrow edema within the augmented vertebral body in 3 cases. We did not find any new bone marrow edema and no new fractures in adjacent and remote segments after balloon kyphoplasty treatment. Conclusion: Prone position leads to no new bone marrow edema and no new fractures in the osteoporotic spine. Accordingly, prone position has no risk for adjacent level fractures in osteoporotic spines. PMID:26504728

Expression of TGF-β in Fractures Fixed by Nitinol Swan-like Memory Compressive Connectors

NASA Astrophysics Data System (ADS)

Li, M.; Zhang, C. C.; Xu, S. G.; Fu, Q. G.

2011-07-01

In this article, the effect of internal fixation of a Nitinol swan-like memory compressive connector (SMC) on the temporal expression of transforming growth factor-β (TGF-β) at fracture sites is evaluated. Specimens were collected from 35 New Zealand rabbits modeled for bilateral humeral fracture fixed with either SMC or stainless dynamic compression plate (DCP). Five rabbits each were killed at day 1, 3, 7, 14, 21, 28, and 56. The local positive staining potency, positive area ratio, and positive index of TGF-β were measured using an immunohistochemistry approach (EnVision) in combination with a computerized image analysis system. TGF-β staining was seen in mesenchymal cells, osteoblasts, chondrocytes, and in the extracellular matrix of fractures fixed in both the SMC and the DCP samples without a significant difference in staining at both the early stages (days 1 and 3) and day 56. A higher TGF-β content was observed in the fractures fixed with SMC when compared to that of DCP from day 7 to 28. As a conclusion, TGF-β is highly expressed in fractures fixed with SMC during chondrogenesis stage and entochondrostosis stage. Finally, the mechanism of how SMC promoting synthesis and secretion of TGF-β in the process of fracture healing has been discussed.

A novel ex vivo model of compressive immature rib fractures at pathophysiological rates of loading.

PubMed

Beadle, Nicola; Burnett, Timothy L; Hoyland, Judith A; Sherratt, Michael J; Freemont, Anthony J

2015-11-01

Compressive rib fractures are considered to be indicative of non-accidental injury (NAI) in infants, which is a significant and growing issue worldwide. The diagnosis of NAI is often disputed in a legal setting, and as a consequence there is a need to model such injuries ex vivo in order to characterise the forces required to produce non-accidental rib fractures. However, current models are limited by type of sample, loading method and rate of loading. Here, we aimed to: i) develop a loading system for inducing compressive fractures in whole immature ribs that is more representative of the physiological conditions and mechanism of injury employed in NAI and ii) assess the influence of loading rate and rib geometry on the mechanical performance of the tissue. Porcine ribs (5-6 weeks of age) from 12 animals (n=8 ribs/animal) were subjected to axial compressive load directed through the anterior-posterior rib axis at loading rates of 1, 30, 60 or 90 mm/s. Key mechanical parameters (including peak load, load and percentage deformation to failure and effective stiffness) were quantified from the load-displacement curves. Measurements of the rib length, thickness at midpoint, distance between anterior and posterior extremities, rib curvature and fracture location were determined from radiographs. This loading method typically produced incomplete fractures around the midpoint of the ribs, with 87% failing in this manner; higher loads and less deformation were required for ribs to completely fracture through both cortices. Loading rate, within the range of 1-90 mm/s, did not significantly affect any key mechanical parameters of the ribs. Load-displacement curves displaying characteristic and quantifiable features were produced for 90% of the ribs tested, and multiple regression analyses indicate that, in addition to the geometrical variables, there are other factors such as the micro- and nano-structure that influence the measured mechanical data. A reproducible method of inducing fractures in a consistent location in immature porcine ribs has been successfully developed. Fracture appearance may be indicative of the amount of load and deformation that produced the fracture, which is an important finding for NAI, where knowledge of the aetiology of fractures is vital. Characteristic rib behaviour independent of loading rate and, to an extent, rib geometry has been demonstrated, allowing further investigation into how the complex micro- and nano-structure of immature ribs influences the mechanical performance under compressive load. This research will ultimately enable improved characterisation of the loading pattern involved in non-accidental rib fractures. Copyright © 2015 Elsevier Ltd. All rights reserved.

Posterior locked lateral compression injury of the pelvis in geriatric patients: an infrequent and specific variant of the fragility fracture of pelvis.

PubMed

Lee, Se-Won; Kim, Weon-Yoo; Koh, Sung-Jun; Kim, Young-Yul

2017-09-01

Posterior locked lateral compression injury (PLLCI) of the pelvic ring is an infrequent variant of lateral compression injury, a condition described in only eight reported cases since 2000. Lateral compression injury usually results from high-energy trauma and is characterized by locking between the medially translated fractured ilium and the anterior border of the sacrum, regardless of whether the fractured ilium involves the sacroiliac joint. However, in our experience, lateral compression injury can also result from low-energy trauma as a manifestation of pelvic fragility fracture. The aim of the present study was to describe this rare form of PLLCI in a case series of geriatric patients. A retrospective analysis of consecutive patients with pelvic ring injuries who were admitted to our hospital from January 2008 to April 2015 identified seven geriatric patients (1 male and 6 females; median age 81 years) with a form of PLLCI. All injuries were due to falls from a standing position onto the ground. All seven cases demonstrated characteristics of a locking fractured ilium over the anterior border of the sacrum on axial computed tomography images, but were not detected on plain radiographs. All underwent follow-up at 1 year or later with improved mean visual analogue scale scores (range 0-3). Regarding Koval walking ability scores, patients who underwent pelvic brim plating with anterior external fixation were more likely to regain their pre-injury walking ability than patients who only underwent anterior external fixation or conservative treatment. Geriatric patients can experience PLCCIs of the pelvis due to low-energy trauma. These fractures have different characteristics from those associated with severe injuries due to high-energy trauma, and they comprise an infrequent form of Rommens fragility fracture of the pelvis (type IIIa). In these cases, appropriate surgical management that includes sacroiliac plating combined with anterior external fixation can yield good outcomes.

Object-Based Mapping of the Circumpolar Taiga-Tundra Ecotone with MODIS Tree Cover

NASA Technical Reports Server (NTRS)

Ranson, K. J.; Montesano, P. M.; Nelson, R.

2011-01-01

The circumpolar taiga tundra ecotone was delineated using an image-segmentation-based mapping approach with multi-annual MODIS Vegetation Continuous Fields (VCF) tree cover data. Circumpolar tree canopy cover (TCC) throughout the ecotone was derived by averaging MODIS VCF data from 2000 to 2005 and adjusting the averaged values using linear equations relating MODIS TCC to Quickbird-derived tree cover estimates. The adjustment helped mitigate VCF's overestimation of tree cover in lightly forested regions. An image segmentation procedure was used to group pixels representing similar tree cover into polygonal features (segmentation objects) that form the map of the transition zone. Each polygon represents an area much larger than the 500 m MODIS pixel and characterizes the patterns of sparse forest patches on a regional scale. Those polygons near the boreal/tundra interface with either (1) mean adjusted TCC values from5 to 20%, or (2) mean adjusted TCC values greater than 5% but with a standard deviation less than 5% were used to identify the ecotone. Comparisons of the adjusted average tree cover data were made with (1) two existing tree line definitions aggregated for each 1 degree longitudinal interval in North America and Eurasia, (2) Landsat-derived Canadian proportion of forest cover for Canada, and (3) with canopy cover estimates extracted from airborne profiling lidar data that transected 1238 of the TCC polygons. The adjusted TCC from MODIS VCF shows, on average, less than 12% TCC for all but one regional zone at the intersection with independently delineated tree lines. Adjusted values track closely with Canadian proportion of forest cover data in areas of low tree cover. A comparison of the 1238 TCC polygons with profiling lidar measurements yielded an overall accuracy of 67.7%.

Prevalence of microdeletion 22q11 in patients with hypernasal speech due to velopharyngeal insufficiency: Expanded phenotype and clinical comparison to nondeletion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siegel-Bartelt, J.; Cytrynbaum, C.; Witzel, M.A.

1994-09-01

Microdeletion 22q11.2 has been reported as a frequent ethiology of both velocardiofacial (VCF) and DiGeorge syndromes. We have studied the prevalence of microdeletion 22q11 in a group of patients ascertained through a Speech and Language clinic presenting with (1) velopharyngeal insufficiency (VPI) and (2) difficultly in school. Growth parameters were measured, and facies were scored for features of VCF. Microdeletions were detected at locus D22S75 by FISH with probe N25 (Oncor), and at 22q11.2 with high resolution banding analysis (HRB). One child with typical VCF facies was considered to have a deletion at 22q11 with HRB, but is not deletedmore » with N25, indicating that N25 may not detect all deletion patients. An additional 8/30 children tested to date were deleted with the N25 probe. Heart defects were present in only 2/8 deletion patients: VSD/ASD and PS/AS. One N25 deletion patient was atypica; he has a tall, lanky habitus (height = 90%), and facies not characteristic of CVF. As expected, there is a trend to lower head size, smaller ear size, and more typical facies in deletion patients; however, four of the nondeletion patients also had a clinical diagnosis of VCF. Medially displaced carotid arteries were present in both groups, which is therefore not a diagnostic feature of microdeletion 22q11. Our findings indicate that the microdeletion 22q11 is frequent (26% in this series) in a population with VPI, even when not selected for typical facies. We believe this series supports the view that microdeletion 22q11 has a broader clinical phenotype than previously recognized.« less

Application of the boundary elements method for modeling of the fracture of cylindrical bodies by hydraulic fracturing

NASA Astrophysics Data System (ADS)

Legan, M. A.; Blinov, V. A.; Larichkin, A. Yu; Novoselov, A. N.

2017-10-01

Experimental study of hydraulic fracturing of thick-walled cylinders with a central circular hole was carried out using the machine that creates a high oil pressure. Experiments on the compression fracture of the solid cylinders by diameter and rectangular parallelepipeds perpendicular to the ends were carried out with a multipurpose test machine Zwick / Roell Z100. Samples were made of GF-177 material based on cement. Ultimate stresses in the material under study were determined for three types of stress state: under compression, with a pure shear on the surface of the hole under frecking conditions and under a compound stress state under conditions of diametral compression of a solid cylinder. The value of the critical stress intensity factor of GF-177 material was obtained. The modeling of the fracturing process taking into account the inhomogeneity of the stress state near the hole was carried out using the boundary elements method (in the variant of the fictitious load method) and the gradient fracture criterion. Calculation results of the ultimate pressure were compared with values obtained analytically on the basis of the Lame solution and with experimental data.

Effect of cements on fracture resistance of monolithic zirconia crowns

PubMed Central

Nakamura, Keisuke; Mouhat, Mathieu; Nergård, John Magnus; Lægreid, Solveig Jenssen; Kanno, Taro; Milleding, Percy; Örtengren, Ulf

2016-01-01

Abstract Objectives The present study investigated the effect of cements on fracture resistance of monolithic zirconia crowns in relation to their compressive strength. Materials and methods Four different cements were tested: zinc phosphate cement (ZPC), glass-ionomer cement (GIC), self-adhesive resin-based cement (SRC) and resin-based cement (RC). RC was used in both dual cure mode (RC-D) and chemical cure mode (RC-C). First, the compressive strength of each cement was tested according to a standard (ISO 9917-1:2004). Second, load-to-failure test was performed to analyze the crown fracture resistance. CAD/CAM-produced monolithic zirconia crowns with a minimal thickness of 0.5 mm were prepared and cemented to dies with each cement. The crown–die samples were loaded until fracture. Results The compressive strength of SRC, RC-D and RC-C was significantly higher than those of ZPC and GIC (p < 0.05). However, there was no significant difference in the fracture load of the crown between the groups. Conclusion The values achieved in the load-to-failure test suggest that monolithic zirconia crowns with a minimal thickness of 0.5 mm may have good resistance against fracture regardless of types of cements. PMID:27335900

Tensile, Compression, Open-Hole Compression and Double Cantilever Beam Fracture Toughness Testing of Multiple NASA Langley Research Center Composite Materials

NASA Technical Reports Server (NTRS)

Adams, Donald F.

1999-01-01

The attached data summarizes the work performed by the Composite Materials Research Group at the University of Wyoming funded by the NASA LaRC Research Grant NAG-1-1294. The work consisted primarily of tension, compression, open-hole compression and double cantilever beam fracture toughness testing performed an a variety of NASA LaRC composite materials. Tests were performed at various environmental conditions and pre-conditioning requirements. The primary purpose of this work was to support the LaRC material development efforts. The data summaries are arranged in chronological order from oldest to newest.

Method for testing the strength and structural integrity of nuclear fuel particles

DOEpatents

Lessing, P.A.

1995-10-17

An accurate method for testing the strength of nuclear fuel particles is disclosed. Each particle includes an upper and lower portion, and is placed within a testing apparatus having upper and lower compression members. The upper compression member includes a depression therein which is circular and sized to receive only part of the upper portion of the particle. The lower compression member also includes a similar depression. The compression members are parallel to each other with the depressions therein being axially aligned. The fuel particle is then placed between the compression members and engaged within the depressions. The particle is then compressed between the compression members until it fractures. The amount of force needed to fracture the particle is thereafter recorded. This technique allows a broader distribution of forces and provides more accurate results compared with systems which distribute forces at singular points on the particle. 13 figs.

Method for testing the strength and structural integrity of nuclear fuel particles

DOEpatents

Lessing, Paul A.

1995-01-01

An accurate method for testing the strength of nuclear fuel particles. Each particle includes an upper and lower portion, and is placed within a testing apparatus having upper and lower compression members. The upper compression member includes a depression therein which is circular and sized to receive only part of the upper portion of the particle. The lower compression member also includes a similar depression. The compression members are parallel to each other with the depressions therein being axially aligned. The fuel particle is then placed between the compression members and engaged within the depressions. The particle is then compressed between the compression members until it fractures. The amount of force needed to fracture the particle is thereafter recorded. This technique allows a broader distribution of forces and provides more accurate results compared with systems which distribute forces at singular points on the particle.

Incorporating Scale-Dependent Fracture Stiffness for Improved Reservoir Performance Prediction

NASA Astrophysics Data System (ADS)

Crawford, B. R.; Tsenn, M. C.; Homburg, J. M.; Stehle, R. C.; Freysteinson, J. A.; Reese, W. C.

2017-12-01

We present a novel technique for predicting dynamic fracture network response to production-driven changes in effective stress, with the potential for optimizing depletion planning and improving recovery prediction in stress-sensitive naturally fractured reservoirs. A key component of the method involves laboratory geomechanics testing of single fractures in order to develop a unique scaling relationship between fracture normal stiffness and initial mechanical aperture. Details of the workflow are as follows: tensile, opening mode fractures are created in a variety of low matrix permeability rocks with initial, unstressed apertures in the micrometer to millimeter range, as determined from image analyses of X-ray CT scans; subsequent hydrostatic compression of these fractured samples with synchronous radial strain and flow measurement indicates that both mechanical and hydraulic aperture reduction varies linearly with the natural logarithm of effective normal stress; these stress-sensitive single-fracture laboratory observations are then upscaled to networks with fracture populations displaying frequency-length and length-aperture scaling laws commonly exhibited by natural fracture arrays; functional relationships between reservoir pressure reduction and fracture network porosity, compressibility and directional permeabilities as generated by such discrete fracture network modeling are then exported to the reservoir simulator for improved naturally fractured reservoir performance prediction.

Transitioning to an Intramedullary Lengthening and Compression Nail

PubMed Central

2017-01-01

Summary: The magnetic intramedullary lengthening nail is an innovative technology that allows for creative ways to treat difficult problems. The lengthening option has revolutionized femur fracture management with bone loss and malunion therapy. The compression version of this nail has provided a gradual method to compress nonunions and difficult fractures that may obviate the need for many current uses of external fixation. Three cases are presented in this manuscript demonstrating a new paradigm in the management of bone loss/shortening of the tibia and femur, and recalcitrant nonunions. PMID:28486284

Kyphoplasty for vertebral augmentation in the elderly with osteoporotic vertebral compression fractures: scenarios and review of recent studies.

PubMed

Bednar, Timothy; Heyde, Christoph E; Bednar, Grace; Nguyen, David; Volpi, Elena; Przkora, Rene

2013-11-01

Vertebral compression fractures caused by osteoporosis are among the most common fractures in the elderly. The treatment focuses on pain control, maintenance of independence, and management of the osteoporosis. Elderly patients often encounter adverse effects to pain medications, do not tolerate bed rest, and are not ideal candidates for invasive spinal reconstructive surgery. Percutaneous vertebral augmentation (vertebroplasty or kyphoplasty) has become popular as a less-invasive alternative. However, studies have questioned the effectiveness of these procedures. The authors conducted a MEDLINE search using relevant search terms including osteoporosis, osteoporotic vertebral compression fracture, elderly, kyphoplasty and vertebroplasty. Two elderly patients presented with a fracture of their third and first lumbar vertebral body, respectively. One patient progressed well with conservative treatment, whereas the other patient was hospitalized secondary to pain after conservative measures failed to offer improvement. The hospitalized patient subsequently opted for a kyphoplasty and was able to resume his normal daily activities after the procedure. Selecting patients on an individual case-by-case basis can optimize the effectiveness and outcomes of a vertebral augmentation. This process includes the documentation of an osteoporotic vertebral compression fracture with the aide of imaging studies, including the acuity of the fracture as well as the correlation with the physical examination findings. Patients who are functional and improving under a conservative regimen are not candidates for kyphoplasty. However, if the conservative management is not successful after 4 to 6 weeks and the patient is at risk to become bedridden, an augmentation should be considered. A kyphoplasty procedure may be preferred over vertebroplasty, given the lower risk profile and better outcomes regarding spinal alignment. Published by Elsevier HS Journals, Inc.

Compression stockings in the management of fractures of the ankle: a randomised controlled trial.

PubMed

Sultan, M J; Zhing, T; Morris, J; Kurdy, N; McCollum, C N

2014-08-01

In this randomised controlled trial, we evaluated the role of elastic compression using ankle injury stockings (AIS) in the management of fractures of the ankle. A total of 90 patients with a mean age of 47 years (16 to 79) were treated within 72 hours of presentation with a fracture of the ankle, 31 of whom were treated operatively and 59 conservatively, were randomised to be treated either with compression by AIS plus an Aircast boot or Tubigrip plus an Aircast boot. Male to female ratio was 36:54. The primary outcome measure was the functional Olerud-Molander ankle score (OMAS). The secondary outcome measures were; the American Orthopaedic Foot and Ankle Society score (AOFAS); the Short Form (SF)-12v2 Quality of Life score; and the frequency of deep vein thrombosis (DVT). Compression using AIS reduced swelling of the ankle at all time points and improved the mean OMAS score at six months to 98 (95% confidence interval (CI) 96 to 99) compared with a mean of 67 (95% CI 62 to 73) for the Tubigrip group (p < 0.001). The mean AOFAS and SF-12v2 scores at six months were also significantly improved by compression. Of 86 patients with duplex imaging at four weeks, five (12%) of 43 in the AIS group and ten (23%) of 43 in the Tubigrip group developed a DVT (p = 0.26). Compression improved functional outcome and quality of life following fracture of the ankle. DVTs were frequent, but a larger study would be needed to confirm that compression with AISs reduces the incidence of DVT. ©2014 The British Editorial Society of Bone & Joint Surgery.

A biomechanical comparison of conventional dynamic compression plates and string-of-pearls™ locking plates using cantilever bending in a canine Ilial fracture model.

PubMed

Kenzig, Allison R; Butler, James R; Priddy, Lauren B; Lacy, Kristen R; Elder, Steven H

2017-07-13

Fracture of the ilium is common orthopedic injury that often requires surgical stabilization in canine patients. Of the various methods of surgical stabilization available, application of a lateral bone plate to the ilium is the most common method of fixation. Many plating options are available, each having its own advantages and disadvantages. The purpose of this study was to evaluate the biomechanical properties of a 3.5 mm String-of-Pearls™ plate and a 3.5 mm dynamic compression plate in a cadaveric canine ilial fracture model. Hemipelves were tested in cantilever bending to failure and construct stiffness, yield load, displacement at yield, ultimate load, and mode of failure were compared. The mean stiffness of dynamic compression plate (116 ± 47 N/mm) and String-of-Pearls™ plate (107 ± 18 N/mm) constructs, mean yield load of dynamic compression plate (793 ± 333 N) and String-of-Pearls™ plate (860 ± 207 N) constructs, mean displacement at yield of dynamic compression plate (8.6 ± 3.0 mm) and String-of-Pearls™ plate (10.2 ± 2.8 mm) constructs, and ultimate load at failure of dynamic compression plate (936 ± 320 N) and String-of-Pearls™ plate (939 ± 191 N) constructs were not significantly different. No differences were found between constructs with respect to mode of failure. No significant biomechanical differences were found between String-of-Pearls™ plate and dynamic compression plate constructs in this simplified cadaveric canine ilial fracture model.

Biochemical Markers of Bone Turnover in Percutaneous Vertebroplasty for Osteoporotic Compression Fracture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komemushi, Atsushi, E-mail: kome64@yo.rim.or.jp; Tanigawa, Noboru; Kariya, Shuji

Purpose. To evaluate relationships between biochemical markers of bone turnover, bone mineral density, and new compression fractures following vertebroplasty. Methods. Initially, we enrolled 30 consecutive patients with vertebral compression fractures caused by osteoporosis. Twenty-three of the 30 patients visited our hospital for follow-up examinations for more than 4 weeks after vertebroplasty. The patients were divided into two groups: patients with new fractures (group F) and patients with no new fractures (group N). We analyzed differences in the following parameters between these two groups: serum bone alkaline phosphatase, urinary crosslinked N-telopeptide of type I collagen, urinary deoxypyridinoline, and bone mineral density.more » Next, the patients were divided into another two groups: patients with higher risk (group H: urinary crosslinked N-telopeptide of type I collagen >54.3 nmol BCE/mmol Cr or urinary deoxypyridinoline >7.6 nmol/mmol Cr, and serum bone alkaline phosphatase <29.0 U/l) and patients with lower risk (group L). We analyzed the difference in the rate of new fractures between these two groups. Results. We identified 9 new fractures in 7 patients. There were no significant differences between groups F and N. We identified 5 new fractures in 3 of the 4 patients in group H, and 4 new fractures in 4 of the 19 patients in group L. There was a significant difference in the rate of new fractures between groups H and L. Conclusions. A combination of high levels of bone resorption markers and normal levels of bone formation markers may be associated with increased risk of new recurrent fractures after percutaneous vertebroplasty.« less

Size Effects on Deformation and Fracture of Scandium Deuteride Films.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teresi, C. S.; Hintsala, E.; Adams, David P.

Metal hydride films have been observed to crack during production and use, prompting mechanical property studies of scandium deuteride films. The following focuses on elastic modulus, fracture, and size effects observed in the system for future film mechanical behavior modeling efforts. Scandium deuteride films were produced through the deuterium charging of electron beam evaporated scandium films using X-ray diffraction, scanning Auger microscopy, and electron backscatter diffraction to monitor changes in the films before and after charging. Scanning electron microscopy, nanoindentation, and focused ion beam machined micropillar compression tests were used for mechanical characterization of the scandium deuteride films. The micropillarsmore » showed a size effect for flow stress, indicating that film thickness is a relevant tuning parameter for film performance, and that fracture was controlled by the presence of grain boundaries. Elastic modulus was determined by both micropillar compression and nanoindentation to be approximately 150 GPa, Fracture studies of bulk film channel cracking as well as compression induced cracks in some of the pillars yielded a fracture toughness around 1.0 MPa-m1/2. Preliminary Weibull distributions of fracture in the micropillars are provided. Despite this relatively low value of fracture toughness, scandium deuteride micropillars can undergo a large degree of plasticity in small volumes and can harden to some degree, demonstrating the ductile and brittle nature of this material« less

Locking Compression Plate in Distal Femoral Intra-Articular Fractures: Our Experience

PubMed Central

Kiran Kumar, G. N.; Sharma, Gaurav; Farooque, Kamran; Sharma, Vijay; Ratan, Ratnav; Yadav, Sanjay; Lakhotia, Devendra

2014-01-01

Background. Intra-articular fractures of distal femur present a huge surgical challenge. The aim of this study is to evaluate functional outcome, fracture healing, and the complications of distal femoral intra-articular fractures using locking compression plates. Material and Methods. We reviewed 46 distal femoral fractures treated with distal femoral locking compression plates between 2009 to 2012. There were 36 men and 10 women with mean age of 35 years (range 20–72). More than half of the patients were of type C3 (AO classification) and had been caused by high energy trauma with associated injuries. Results. 2 patients were lost to follow-up. Of the remaining 44 patients, the mean follow-up period was 25 months (range 18–36). The mean time for radiological union was 12 weeks (range 10–18) except 2 patients which had gone for nonunion. At the latest follow up ROM >120° is noted in 32 patients, 90–120 in 10 patients, and 70–90 in 2 patients. 38 patients (86%) had good/excellent outcome. Conclusion. Use of standard lateral approach for simple intra-articular distal femoral fractures (C1) and transarticular/minimally invasive techniques for complex intra-articular fractures (C2/C3) results in improved exposure of the knee joint and better union rates with low incidence of bone grafting. PMID:27355064

An efficient numerical model for multicomponent compressible flow in fractured porous media

NASA Astrophysics Data System (ADS)

Zidane, Ali; Firoozabadi, Abbas

2014-12-01

An efficient and accurate numerical model for multicomponent compressible single-phase flow in fractured media is presented. The discrete-fracture approach is used to model the fractures where the fracture entities are described explicitly in the computational domain. We use the concept of cross flow equilibrium in the fractures. This will allow large matrix elements in the neighborhood of the fractures and considerable speed up of the algorithm. We use an implicit finite volume (FV) scheme to solve the species mass balance equation in the fractures. This step avoids the use of Courant-Freidricks-Levy (CFL) condition and contributes to significant speed up of the code. The hybrid mixed finite element method (MFE) is used to solve for the velocity in both the matrix and the fractures coupled with the discontinuous Galerkin (DG) method to solve the species transport equations in the matrix. Four numerical examples are presented to demonstrate the robustness and efficiency of the proposed model. We show that the combination of the fracture cross-flow equilibrium and the implicit composition calculation in the fractures increase the computational speed 20-130 times in 2D. In 3D, one may expect even a higher computational efficiency.

[Complications of percutaneous kyphoplasty non-related with bone leakage in treating osteoporotic thoracolumbar vertebral compression fractures].

PubMed

Ru, Xuan-liong; Jiang, Zeng-hui; Gui, Xian-ge; Sun, Qi-cai; Song, Bo-Shan; Lin, Hang; He, Jian

2015-08-01

To analyze the complications of percutaneous kyphoplasty except bone leakge for the treatment of osteoporotic thoracolumbar vertebral compression fractures. From October 2008 to October 2012,178 patients with 224 osteoporotic vertebral compression fractures were treated with percutaneous kyphoplasty under local anethsia. There were 72 males and 106 females,ranging in age from 58 to 92 years old,with an average of 75.3 years,including 93 thoracic vertebrae and 131 lumbar vertebrae. The complications except bone cement leakage were analyzed during operation and after operation. All operations were successful and all patients were followed up from 12 to 60 months with an average of 26.2 months. No death was found. Bone cement leakage occurred in 27 cases, about 15.1% in 178 cases; and complications except bone cement leakage occurred in 15 cases. There was 1 case with cardiac arrest,was completely recovery by cardiopulmonary resuscitation (CPR) immediately; and 1 case with temporary absence of breathing,was recovery after treatment. There were 3 cases with fall of blood pressure and slower of heart rate; 1 case with intestinal obstruction; 2 cases with local hematoma and 1 case with intercostal neuralgia. Vertebral body fractures of 2 cases were split by bone cement and the fractures of adjacent body occurred in 4 cases. It's uncommon complication except bone cement leakge in treatment of osteoporotic thoracolumbar vertebral compression fractures with percutaneous kyphoplasty. The complication of cardiopulmonary system is a high risk in surgery; and cytotoxicity of bone cement,nervous reflex,fat embolism and alteration of intravertebral pressure may be main reasons.

Tension band wiring of the olecranon: is it really a dynamic principle of osteosynthesis?

PubMed

Brink, P R G; Windolf, M; de Boer, P; Brianza, S; Braunstein, V; Schwieger, K

2013-04-01

The tension band principle as applied to transverse olecranon fractures fixed by tension band wiring is based on the premise that distraction forces on the outer cortex of the ulna during elbow flexion are converted to compression forces on the articular surface of the olecranon at the fracture site. In view of some clinical outcomes, where hardware failure and secondary dislocations occur, the question arises if the dynamic compression theory is correct. Compressive forces during active flexion and extension after tension band wiring of a transverse osteotomy of the olecranon were measured in 6 fresh frozen human cadaveric models using a pressure-sensor in the osteotomy gap. We could collect 30 measurements during active flexion and 30 during active extension. Active flexion did not cause any compressive forces in the osteotomy gap. Extension with the humerus in an upright position and the elbow actively extended causes some compression (0.37-0.51 MPa) at the articular surface comparing with active flexion (0.2 MPa) due to gravity forces. Posterior, there was no significant pressure difference observed (0.41-0.45 versus 0.36-0.32 MPa) between active flexion and extension. The tension band wiring principle only exists during active extension in a range of 30-120° of flexion of the elbow. Postoperative exercise programs should be modified in order to prevent loss of compression at the fracture site of transverse olecranon fractures, treated with tension band wiring when the elbow is mobilised. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biomechanics of bone-fracture fixation by stiffness-graded plates in comparison with stainless-steel plates

PubMed Central

Ganesh, VK; Ramakrishna, K; Ghista, Dhanjoo N

2005-01-01

Background In the internal fixation of fractured bone by means of bone-plates fastened to the bone on its tensile surface, an on-going concern has been the excessive stress-shielding of the bone by the excessively-stiff stainless-steel plate. The compressive stress-shielding at the fracture-interface immediately after fracture-fixation delays callus formation and bone healing. Likewise, the tensile stress-shielding of the layer of the bone underneath the plate can cause osteoporosis and decrease in tensile strength of this layer. Method In order to address this problem, we propose to use stiffness-graded plates. Accordingly, we have computed (by finite-element analysis) the stress distribution in the fractured bone fixed by composite plates, whose stiffness is graded both longitudinally and transversely. Results It can be seen that the stiffness-graded composite-plates cause less stress-shielding (as an example: at 50% of the healing stage, stress at the fracture interface is compressive in nature i.e. 0.002 GPa for stainless steel plate whereas stiffness graded plates provides tensile stress of 0.002 GPa. This means that stiffness graded plate is allowing the 50% healed bone to participate in loadings). Stiffness-graded plates are more flexible, and hence permit more bending of the fractured bone. This results in higher compressive stresses induced at the fractured faces accelerate bone-healing. On the other hand, away from the fracture interface the reduced stiffness and elastic modulus of the plate causes the neutral axis of the composite structure to be lowered into the bone resulting in the higher tensile stress in the bone-layer underneath the plate, wherein is conducive to the bone preserving its tensile strength. Conclusion Stiffness graded plates (with in-built variable stiffness) are deemed to offer less stress-shielding to the bone, providing higher compressive stress at the fractured interface (to induce accelerated healing) as well as higher tensile stress in the intact portion of the bone (to prevent bone remodeling and osteoporosis). PMID:16045807

Effects of age and loading rate on equine cortical bone failure.

PubMed

Kulin, Robb M; Jiang, Fengchun; Vecchio, Kenneth S

2011-01-01

Although clinical bone fractures occur predominantly under impact loading (as occurs during sporting accidents, falls, high-speed impacts or other catastrophic events), experimentally validated studies on the dynamic fracture behavior of bone, at the loading rates associated with such events, remain limited. In this study, a series of tests were performed on femoral specimens obtained post-mortem from equine donors ranging in age from 6 months to 28 years. Fracture toughness and compressive tests were performed under both quasi-static and dynamic loading conditions in order to determine the effects of loading rate and age on the mechanical behavior of the cortical bone. Fracture toughness experiments were performed using a four-point bending geometry on single and double-notch specimens in order to measure fracture toughness, as well as observe differences in crack initiation between dynamic and quasi-static experiments. Compressive properties were measured on bone loaded parallel and transverse to the osteonal growth direction. Fracture propagation was then analyzed using scanning electron and scanning confocal microscopy to observe the effects of microstructural toughening mechanisms at different strain rates. Specimens from each horse were also analyzed for dry, wet and mineral densities, as well as weight percent mineral, in order to investigate possible influences of composition on mechanical behavior. Results indicate that bone has a higher compressive strength, but lower fracture toughness when tested dynamically as compared to quasi-static experiments. Fracture toughness also tends to decrease with age when measured quasi-statically, but shows little change with age under dynamic loading conditions, where brittle "cleavage-like" fracture behavior dominates. Copyright © 2010 Elsevier Ltd. All rights reserved.

Impact Processes in the Solar System

NASA Technical Reports Server (NTRS)

Ahrens, Thomas J.

2004-01-01

Our laboratory has previously conducted impact fracture and dynamic failure tests. Polanskey and Ahrens [1990] mapped the fractures from a series of laboratory craters (Fig. 1) and Ahrens and Rubin [ 1993] inferred that the usually further extending radial cracks resulted from tensional failure during the compression of the shock propagation. The radial spreading induced by the particle velocity field caused the stresses perpendicular to the shock front to become sufficiently large and tensile. This induces "radial fractures." The concentric fractures are attributed to the tensional failure occurring after the initial compressive phase. Upon radial propagation of the stress wave the negative tension behind the stress-wave front caused failure along the quasi-spherical concentric fractures. The near-surface and spall fractures are attributed to the fractures described by Melosh [1984]. These are activated by impact and can launch relatively unshocked samples of planetary surfaces to speeds exceeding escape velocity. In the case of Mars, some of these surface samples presumably become the SNC (Mars) meteorites.

Vertebral Augmentation Involving Vertebroplasty or Kyphoplasty for Cancer-Related Vertebral Compression Fractures: An Economic Analysis.

PubMed

2016-01-01

Untreated vertebral compression fractures can have serious clinical consequences and impose a considerable impact on patients' quality of life and on caregivers. Since non-surgical management of these fractures has limited effectiveness, vertebral augmentation procedures are gaining acceptance in clinical practice for pain control and fracture stabilization. The objective of this analysis was to determine the cost-effectiveness and budgetary impact of kyphoplasty or vertebroplasty compared with non-surgical management for the treatment of vertebral compression fractures in patients with cancer. We performed a systematic review of health economic studies to identify relevant studies that compare the cost-effectiveness of kyphoplasty or vertebroplasty with non-surgical management for the treatment of vertebral compression fractures in adults with cancer. We also performed a primary cost-effectiveness analysis to assess the clinical benefits and costs of kyphoplasty or vertebroplasty compared with non-surgical management in the same population. We developed a Markov model to forecast benefits and harms of treatments, and corresponding quality-adjusted life years and costs. Clinical data and utility data were derived from published sources, while costing data were derived using Ontario administrative sources. We performed sensitivity analyses to examine the robustness of the results. In addition, a 1-year budget impact analysis was performed using data from Ontario administrative sources. Two scenarios were explored: (a) an increase in the total number of vertebral augmentation procedures performed among patients with cancer in Ontario, maintaining the current proportion of kyphoplasty versus vertebroplasty; and (b) no increase in the total number of vertebral augmentation procedures performed among patients with cancer in Ontario but an increase in the proportion of kyphoplasties versus vertebroplasties. The base case considered each of kyphoplasty and vertebroplasty versus non-surgical management. Kyphoplasty and vertebroplasty were associated with an incremental cost-effectiveness ratio of $33,471 and $17,870, respectively, per quality-adjusted life-year gained. The budgetary impact of funding vertebral augmentation procedures for the treatment of vertebral compression fractures in adults with cancer in Ontario was estimated at about $2.5 million in fiscal year 2014/15. More widespread use of vertebral augmentation procedures raised total expenditures under a number of scenarios, with costs increasing by $67,302 to $913,386. Our findings suggest that the use of kyphoplasty or vertebroplasty in the management of vertebral compression fractures in patients with cancer may be a cost-effective strategy at commonly accepted willingness-to-pay thresholds. Nonetheless, more widespread use of kyphoplasty (and vertebroplasty to a lesser extent) would likely be associated with net increases in health care costs.

[Contact characteristics research of acetabular weight-bearing area with different internal fixation methods after compression fracture of acetabular dome].

PubMed

Xu, Bowen; Zhang, Qingsong; An, Siqi; Pei, Baorui; Wu, Xiaobo

2017-08-01

To establish the model of compression fracture of acetabular dome, and to measure the contact characteristics of acetabular weight-bearing area of acetabulum after 3 kinds of internal fixation. Sixteen fresh adult half pelvis specimens were randomly divided into 4 groups, 4 specimens each group. Group D was the complete acetabulum (control group), and the remaining 3 groups were prepared acetabular dome compression fracture model. The fractures were fixed with reconstruction plate in group A, antegrade raft screws in group B, and retrograde raft screws in group C. The pressure sensitive films were attached to the femoral head, and the axial compression test was carried out on the inverted single leg standing position. The weight-bearing area, average stress, and peak stress were measured in each group. Under the loading of 500 N, the acetabular weight-bearing area was significantly higher in group D than in other 3 groups ( P <0.05), and the average stress and peak stress were significantly lower than in other 3 groups ( P <0.05). The acetabular weight-bearing area were significantly higher in group B and group C than in group A, and the average stress and peak stress were significantly lower than in group A ( P <0.05). There was no significant difference in the above indexes between group B and group C ( P >0.05). For the compression fracture of the acetabular dome, the contact characteristics of the weight-bearing area can not restore to the normal level, even if the anatomical reduction and rigid internal fixation were performed; compared with the reconstruction plate fixation, antegrade and retrograde raft screws fixations can increase the weight-bearing area, reduce the average stress and peak stress, and reduce the incidence of traumatic arthritis.

History of internal fixation with plates (part 2): new developments after World War II; compressing plates and locked plates.

PubMed

Hernigou, Philippe; Pariat, Jacques

2017-07-01

The first techniques of operative fracture with plates were developed in the 19th century. In fact, at the beginning these methods consisted of an open reduction of the fracture usually followed by a very unstable fixation. As a consequence, the fracture had to be opened with a real risk of (sometimes lethal) infection, and due to unstable fixation, protection with a cast was often necessary. During the period between World Wars I and II, plates for fracture fixation developed with great variety. It became increasingly recognised that, because a fracture of a long bone normally heals with minimal resorption at the bone ends, this may result in slight shortening and collapse, so a very rigid plate might prevent such collapse. However, as a consequence, delayed healing was observed unless the patient was lucky enough to have the plate break. One way of dealing with this was to use a slotted plate in which the screws could move axially, but the really important advance was recognition of the role of compression. After the first description of compression by Danis with a "coapteur", Bagby and Müller with the AO improved the technique of compression. The classic dynamic compression plates from the 1970s were the key to a very rigid fixation, leading to primary bone healing. Nevertheless, the use of strong plates resulted in delayed union and the osteoporosis, cancellous bone, comminution, and/or pathological bone resulted in some failures due to insufficient stability. Finally, new devices represented by locking plates increased the stability, contributing to the principles of a more biological osteosynthesis while giving enough stability to allow immediate full weight bearing in some patients.

The effect of osteoporotic vertebral fracture on predicted spinal loads in vivo.

PubMed

Briggs, Andrew M; Wrigley, Tim V; van Dieën, Jaap H; Phillips, Bev; Lo, Sing Kai; Greig, Alison M; Bennell, Kim L

2006-12-01

The aetiology of osteoporotic vertebral fractures is multi-factorial, and cannot be explained solely by low bone mass. After sustaining an initial vertebral fracture, the risk of subsequent fracture increases greatly. Examination of physiologic loads imposed on vertebral bodies may help to explain a mechanism underlying this fracture cascade. This study tested the hypothesis that model-derived segmental vertebral loading is greater in individuals who have sustained an osteoporotic vertebral fracture compared to those with osteoporosis and no history of fracture. Flexion moments, and compression and shear loads were calculated from T2 to L5 in 12 participants with fractures (66.4 +/- 6.4 years, 162.2 +/- 5.1 cm, 69.1 +/- 11.2 kg) and 19 without fractures (62.9 +/- 7.9 years, 158.3 +/- 4.4 cm, 59.3 +/- 8.9 kg) while standing. Static analysis was used to solve gravitational loads while muscle-derived forces were calculated using a detailed trunk muscle model driven by optimization with a cost function set to minimise muscle fatigue. Least squares regression was used to derive polynomial functions to describe normalised load profiles. Regression co-efficients were compared between groups to examine differences in loading profiles. Loading at the fractured level, and at one level above and below, were also compared between groups. The fracture group had significantly greater normalised compression (p = 0.0008) and shear force (p < 0.0001) profiles and a trend for a greater flexion moment profile. At the level of fracture, a significantly greater flexion moment (p = 0.001) and shear force (p < 0.001) was observed in the fracture group. A greater flexion moment (p = 0.003) and compression force (p = 0.007) one level below the fracture, and a greater flexion moment (p = 0.002) and shear force (p = 0.002) one level above the fracture was observed in the fracture group. The differences observed in multi-level spinal loading between the groups may explain a mechanism for increased risk of subsequent vertebral fractures. Interventions aimed at restoring vertebral morphology or reduce thoracic curvature may assist in normalising spine load profiles.

[Utility of nickel-titanium shape memory alloys of vertebral body reduction fixator with assisted distraction bar].

PubMed

Man, Yi; Zheng, Yue-huan; Cao, Peng; Chen, Bo; Zheng, Tao; Sun, Chang-hui; Lu, Jiong

2011-06-07

To test the nickel-titanium (Ni-Ti) shape memory alloys of vertebral body reduction fixator with assisted distraction bar for the treatment of traumatic and osteoporotic vertebral body fracture. A Ni-Ti shape memory alloys of vertebral body reduction fixator with assisted distraction bar was implanted into the compressed fracture specimens through vertebral pedicle with the radiographic monitoring to reduce the collapsed endplate as well as distract the compressed vertebral fracture. Radiographic film and computed tomographic reconstruction technique were employed to evaluate the effects of reduction and distraction. A biomechanic test machine was used to measure the fatigue and the stability of deformation of fixation segments. Relying on the effect of temperature shape memory, such an assembly could basically reduce the collapsed endplate as well as distract the compressed vertebral fracture. And when unsatisfied results of reduction and distraction occurred, its super flexibility could provide additional distraction strength. A Ni-Ti shape memory alloys of vertebral body reduction fixator with assisted distraction bar may provide effective endplate reduction, restore the vertebral height and the immediate biomechanic spinal stability. So the above assembly is indicated for the treatment of traumatic and osteoporotic vertebral body fracture.

A prospective, randomised trial comparing closed intramedullary nailing with percutaneous plating in the treatment of distal metaphyseal fractures of the tibia.

PubMed

Guo, J J; Tang, N; Yang, H L; Tang, T S

2010-07-01

We compared the outcome of closed intramedullary nailing with minimally invasive plate osteosynthesis using a percutaneous locked compression plate in patients with a distal metaphyseal fracture in a prospective study. A total of 85 patients were randomised to operative stabilisation either by a closed intramedullary nail (44) or by minimally invasive osteosynthesis with a compression plate (41). Pre-operative variables included the patients' age and the side and pattern of the fracture. Peri-operative variables were the operating time and the radiation time. Postoperative variables were wound problems, the time to union of the fracture, the functional American Orthopaedic Foot and Ankle surgery score and removal of hardware. We found no significant difference in the pre-operative variables or in the time to union in the two groups. However, the mean radiation time and operating time were significantly longer in the locked compression plate group (3.0 vs 2.12 minutes, p < 0.001, and 97.9 vs 81.2 minutes, p < 0.001, respectively).After one year, all the fractures had united. Patients who had intramedullary nailing had a higher mean pain score (40 = no pain, 0 = severe pain), [corrected] but better function, alignment and total American Orthopaedic Foot and Ankle surgery scores, although the differences were not statistically significant (p = 0.234, p = 0.157, p = 0.897, p = 0.177 respectively). Three (6.8%) patients in the intramedullary nailing group and six (14.6%) in the locked compression plate group showed delayed wound healing, and 37 (84.1%) in the former group and 38 (92.7%) in the latter group expressed a wish to have the implant removed. We conclude that both closed intramedullary nailing and a percutaneous locked compression plate can be used safely to treat Orthopaedic Trauma Association type-43A distal metaphyseal fractures of the tibia. However, closed intramedullary nailing has the advantage of a shorter operating and radiation time and easier removal of the implant. We therefore prefer closed intramedullary nailing for patients with these fractures.

[APPLICATION OF BUTTERFLY SHAPED LOCKING COMPRESSION PLATE IN COMPLEX DISTAL RADIUS FRACTURES].

PubMed

Jiang, Zongyuan; Ma, Tao; Xia, Jiang; Hu, Caizhi; Xu, Lei

2014-06-01

To investigate the effectiveness of butterfly shaped locking compression plate for the treatment of complex distal radius fractures. Between June 2011 and January 2013, 20 cases of complex distal radius fractures were treated with butterfly shaped locking compression plate fixation. There were 11 males and 9 females with an average age of 54 years (range, 25-75 years). Injury was caused by falling in 10 cases, by traffic accident in 7 cases, and by falling from height in 3 cases. All of fractures were closed. According to AO classification system, there were 8 cases of type C1, 8 cases of type C2, and 4 cases of type C3. Of them, 9 cases had radial styloid process fracture, 4 cases had sigmoid notch fracture, and 7 cases had both radial styloid process fracture and sigmoid notch fracture. The mean interval between injury and operation was 5.2 days (range, 3-15 days). All incisions healed by first intention; no complications of infection and necrosis occurred. All cases were followed up 14 months on average (range, 10-22 months). All factures healed after 9.3 weeks on average (range, 6-11 weeks). No complications such as displacement of fracture, joint surface subsidence, shortening of the radius, and carpal tunnel syndrome were found during follow-up. At last follow-up, the mean palmar tilt angle was 10.2° (range, 7-15°), and the mean ulnar deviation angle was 21.8° (range, 17-24°). The mean range of motion of the wrist was 45.3° (range, 35-68°) in dorsal extension, 53.5° (range, 40-78°) in palmar flexion, 19.8° (range, 12-27°) in radial inclination, 26.6° (range, 18-31°) in ulnar inclination, 70.2° (range, 45-90°) in pronation, and 68.4° (range, 25-88°) in supination. According to the Dienst scoring system, the results were excellent in 8 cases, good in 10 cases, and fair in 2 cases, and the excellent and good rate was 90%. Treatment of complex distal radius fractures with butterfly shaped locking compression plate can reconstruct normal anatomic structures, especially for radial styloid process and sigmoid notch fractures, and it can get good functional recovery of the wrist and the distal radioulnar joint.

Advantages of the Ilizarov external fixation in the management of intra-articular fractures of the distal tibia

PubMed Central

Vasiliadis, Elias S; Grivas, Theodoros B; Psarakis, Spyridon A; Papavasileiou, Evangelos; Kaspiris, Angelos; Triantafyllopoulos, Georgios

2009-01-01

Background Treatment of distal tibial intra-articular fractures is challenging due to the difficulties in achieving anatomical reduction of the articular surface and the instability which may occur due to ligamentous and soft tissue injury. The purpose of this study is to present an algorithm in the application of external fixation in the management of intra-articular fractures of the distal tibia either from axial compression or from torsional forces. Materials and methods Thirty two patients with intra-articular fractures of the distal tibia have been studied. Based on the mechanism of injury they were divided into two groups. Group I includes 17 fractures due to axial compression and group II 15 fractures due to torsional force. An Ilizarov external fixation was used in 15 patients (11 of group I and 4 of group II). In 17 cases (6 of group I and 11 of group II) a unilateral hinged external fixator was used. In 7 out of 17 fractures of group I an additional fixation of the fibula was performed. Results All fractures were healed. The mean time of removal of the external fixator was 11 weeks for group I and 10 weeks for group II. In group I, 5 patients had radiological osteoarthritic lesions (grade III and IV) but only 2 were symptomatic. Delayed union occurred in 3 patients of group I with fixed fibula. Other complications included one patient of group II with subluxation of the ankle joint after removal of the hinged external fixator, in 2 patients reduction found to be insufficient during the postoperative follow up and were revised and 6 patients had a residual pain. The range of ankle joint motion was larger in group II. Conclusion Intra-articular fractures of the distal tibia due to axial compression are usually complicated with cartilaginous problems and are requiring anatomical reduction of the articular surface. Fractures due to torsional forces are complicated with ankle instability and reduction should be augmented with ligament repair, in order to restore normal movement of talus against the mortise. Both Ilizarov and hinged external fixators are unable to restore ligamentous stability. External fixation is recommended only for fractures of the ankle joint caused by axial compression because it is biomechanically superior and has a lower complication rate. PMID:19754962

Dissolved organic matter reduces algal accumulation of methylmercury

USGS Publications Warehouse

Luengen, Allison C.; Fisher, Nicholas S.; Bergamaschi, Brian A.

2012-01-01

Dissolved organic matter (DOM) significantly decreased accumulation of methylmercury (MeHg) by the diatom Cyclotella meneghiniana in laboratory experiments. Live diatom cells accumulated two to four times more MeHg than dead cells, indicating that accumulation may be partially an energy-requiring process. Methylmercury enrichment in diatoms relative to ambient water was measured by a volume concentration factor (VCF). Without added DOM, the maximum VCF was 32 x 104, and the average VCF (from 10 to 72 h) over all experiments was 12.6 x 104. At very low (1.5 mg/L) added DOM, VCFs dropped by approximately half. At very high (20 mg/L) added DOM, VCFs dropped 10-fold. Presumably, MeHg was bound to a variety of reduced sulfur sites on the DOM, making it unavailable for uptake. Diatoms accumulated significantly more MeHg when exposed to transphilic DOM extracts than hydrophobic ones. However, algal lysate, a labile type of DOM created by resuspending a marine diatom in freshwater, behaved similarly to a refractory DOM isolate from San Francisco Bay. Addition of 67 μM L-cysteine resulted in the largest drop in VCFs, to 0.28 x 104. Although the DOM composition influenced the availability of MeHg to some extent, total DOM concentration was the most important factor in determining algal bioaccumulation of MeHg.

Left ventricular performance in various heart diseases with or without heart failure:--an appraisal by quantitative one-plane cineangiocardiography.

PubMed

Lien, W P; Lee, Y S; Chang, F Z; Chen, J J; Shieh, W B

1978-01-01

Quantitative one-plane cineangiocardiography in right anterior oblique position for evaluation of LV performance was carried out in 62 patients with various heart diseases and in 13 subjects with normal LV. Parameters for evaluating both pump and muscle performances were derived from volume and pressure measurements. Of 31 patients with either systolic hypertension or LV myocardial diseases (coronary artery disease or idiopathic cardiomyopathy), 14 had clinical evidence of LV failure before the study. It was found that mean VCF and EF were most sensitive indicators of impaired LV performance among the various parameters. There was a close correlation between mean VCF and EF, yet discordant changes of both parameters were noted in some patients. Furthermore, wall motion abnormalities were not infrequently observed in patients with coronary artery disease or primary cardiomyopathy. Therefore, assessment of at least three ejection properties (EF, mean VCF and wall motion abnormalities) are considered to be essential for full understanding of derangement of LV function in heart disease. This is especially true of patients with coronary artery disease. LV behavior in relation to different pathological stresses or lesions, such as chronic pressure or volume load, myocardial disease and mitral stenosis, was also studied and possible cause of impaired LV myocardial function in mitral stenosis was discussed.

Prediction of Fracture Initiation in Hot Compression of Burn-Resistant Ti-35V-15Cr-0.3Si-0.1C Alloy

NASA Astrophysics Data System (ADS)

Zhang, Saifei; Zeng, Weidong; Zhou, Dadi; Lai, Yunjin

2015-11-01

An important concern in hot working of metals is whether the desired deformation can be accomplished without fracture of the material. This paper builds a fracture prediction model to predict fracture initiation in hot compression of a burn-resistant beta-stabilized titanium alloy Ti-35V-15Cr-0.3Si-0.1C using a combined approach of upsetting experiments, theoretical failure criteria and finite element (FE) simulation techniques. A series of isothermal compression experiments on cylindrical specimens were conducted in temperature range of 900-1150 °C, strain rate of 0.01-10 s-1 first to obtain fracture samples and primary reduction data. Based on that, a comparison of eight commonly used theoretical failure criteria was made and Oh criterion was selected and coded into a subroutine. FE simulation of upsetting experiments on cylindrical specimens was then performed to determine the fracture threshold values of Oh criterion. By building a correlation between threshold values and the deforming parameters (temperature and strain rate, or Zener-Hollomon parameter), a new fracture prediction model based on Oh criterion was established. The new model shows an exponential decay relationship between threshold values and Zener-Hollomon parameter (Z), and the relative error of the model is less than 15%. This model was then applied successfully in the cogging of Ti-35V-15Cr-0.3Si-0.1C billet.

[Effectiveness of long segment fixation combined with vertebroplasty for severe osteoporotic thoracolumbar compressive fractures].

PubMed

Xu, Zixing; Xu, Weihong; Wang, Changsheng; Luo, Hongbin; Li, Guishuang; Chen, Rongsheng

2013-11-01

To study the effectiveness of long segment fixation combined with vertebroplasty (LSF-VP) for severe osteoporotic thoracolumbar compressive fractures with kyphosis deformity. Between March 2006 and May 2012, a retrospective analysis was made on the clinical data of 48 cases of severe osteoporotic thoracolumbar compressive fractures with more than 50% collapse of the anterior vertebral body or more than 400 of sagittal angulation, which were treated by LSF-VP in 27 cases (LSF-VP group) or percutaneous kyphoplasty (PKP) in 21 cases (PKP group). All patients suffered from single thoracolumbar vertebral compressive fracture at T11 to L2. There was no significant difference in gender, age, spinal segment, and T values of bone mineral density between 2 groups (P > 0.05). The effectiveness of the treatment was appraised by visual analogue scale (VAS), Cobb angle of thoracolumbar kyphosis, height of anterior/posterior vertebral body, and compressive ratio of vertebrae before and after operations. The LSF-VP group had longer operation time, hospitalization days, and more bone cement injection volume than the PKP group, showing significant differences (P < 0.05). Intraoperative blood loss in LSF-VP group ranged from 220 to 1,050 mL (mean, 517 mL). No pulmonaryor cerebral embolism or cerebrospinal fluid leakage was found in both groups. Asymptomatic bone cement leakage was found in 3 cases of LSF-VP group and 2 cases of PKP group. The patients were followed up for 16-78 months (mean, 41.1 months) in LSF-VP group, and 12-71 months (mean, 42.1 months) in PKP group. No fixation failure such as loosened or broken pedicle screw was found in LSF-VP group during the follow-up, and no re-fracture or adjacent vertebral body fracture was found. Two cases in PKP group at 39 and 56 months after operation respectively were found to have poor maintenance of vertebral height and loss of rectification (Cobb angle was more than 40 degrees) with recurrence of pain, which were treated by second surgery of LSF-VP; another case had compressive fracture of the adjacent segment and thoracolumbar kyphosis at 16 months after operation, which was treated by second surgery of LSF-VP. There were significant differences in the other indexes between each pair of the three time points (P < 0.05), except the Cobb angle of thoracolumbar kyphosis, and the height of posterior vertebral body between discharge and last follow-up in LSF-VP group, and except the Cobb angle of thoracolumbar kyphosis and compressive ratio of bertebrae between discharge and last follow-up in PKP group (P > 0.05). After operation, the other indexes of LSF-VP group were significantly better than those of PKP group at each time point (P < 0.05), except the VAS score and the height of posterior vertebral body at discharge (P > 0.05). The effectiveness of LSF-VP is satisfactory in treating severe osteoporotic thoracolumbar compressive fractures with kyphosis deformity. LSF-VP can acquire better rectification of kyphosis and recovery of vertebral body height than PKP.

Biomechanics of Thoracolumbar Burst and Chance-Type Fractures during Fall from Height

PubMed Central

Ivancic, Paul C.

2014-01-01

Study Design In vitro biomechanical study. Objective To investigate the biomechanics of thoracolumbar burst and Chance-type fractures during fall from height. Methods Our model consisted of a three-vertebra human thoracolumbar specimen (n = 4) stabilized with muscle force replication and mounted within an impact dummy. Each specimen was subjected to a single fall from an average height of 2.1 m with average velocity at impact of 6.4 m/s. Biomechanical responses were determined using impact load data combined with high-speed movie analyses. Injuries to the middle vertebra of each spinal segment were evaluated using imaging and dissection. Results Average peak compressive forces occurred within 10 milliseconds of impact and reached 40.3 kN at the ground, 7.1 kN at the lower vertebra, and 3.6 kN at the upper vertebra. Subsequently, average peak flexion (55.0 degrees) and tensile forces (0.7 kN upper vertebra, 0.3 kN lower vertebra) occurred between 43.0 and 60.0 milliseconds. The middle vertebra of all specimens sustained pedicle and endplate fractures with comminution, bursting, and reduced height of its vertebral body. Chance-type fractures were observed consisting of a horizontal split fracture through the laminae and pedicles extending anteriorly through the vertebral body. Conclusions We hypothesize that the compression fractures of the pedicles and vertebral body together with burst fracture occurred at the time of peak spinal compression, 10 milliseconds. Subsequently, the onset of Chance-type fracture occurred at 20 milliseconds through the already fractured and weakened pedicles and vertebral body due to flexion-distraction and a forward shifting spinal axis of rotation. PMID:25083357

Intramedullary nailing of humeral shaft fractures.

PubMed

Pickering, Robert M; Crenshaw, Andrew H; Zinar, Daniel M

2002-01-01

The development of interlocking humeral nail systems has greatly broadened the indications for nailing of humeral shaft fracture. Rotational control is better than with earlier nail systems, and most nails have an oblong distal hole that allows axial loading of the fracture site with muscle contraction. When nailing is done with closed technique, loss of the fracture hematoma and periosteal stripping are avoided. Even when open reduction is required, periosteal stripping can be kept to a minimum. Surgical wounds are smaller, even when open reduction is necessary, and when closed nailing is done, bone grafting is unnecessary. Intramedullary nails are ideal for segmental fractures, pathologic fractures, and fractures in osteopenic bone. Because the arm usually is not a weight-bearing extremity, hardware failure is rare and union rates are equivalent to those of compression plate and screw fixation. Compression plates and external fixation certainly have their place for some fracture patterns and for severe wounds that are unsuitable for intramedullary nailing. The surgeon should be well versed in all three techniques and should be able to rapidly choose among these, depending upon the fracture pattern, skin wound, associated injuries, and overall condition of the patient.

Risk Prediction of New Adjacent Vertebral Fractures After PVP for Patients with Vertebral Compression Fractures: Development of a Prediction Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Bin-Yan; He, Shi-Cheng; Zhu, Hai-Dong

PurposeWe aim to determine the predictors of new adjacent vertebral fractures (AVCFs) after percutaneous vertebroplasty (PVP) in patients with osteoporotic vertebral compression fractures (OVCFs) and to construct a risk prediction score to estimate a 2-year new AVCF risk-by-risk factor condition.Materials and MethodsPatients with OVCFs who underwent their first PVP between December 2006 and December 2013 at Hospital A (training cohort) and Hospital B (validation cohort) were included in this study. In training cohort, we assessed the independent risk predictors and developed the probability of new adjacent OVCFs (PNAV) score system using the Cox proportional hazard regression analysis. The accuracy ofmore » this system was then validated in both training and validation cohorts by concordance (c) statistic.Results421 patients (training cohort: n = 256; validation cohort: n = 165) were included in this study. In training cohort, new AVCFs after the first PVP treatment occurred in 33 (12.9%) patients. The independent risk factors were intradiscal cement leakage and preexisting old vertebral compression fracture(s). The estimated 2-year absolute risk of new AVCFs ranged from less than 4% in patients with neither independent risk factors to more than 45% in individuals with both factors.ConclusionsThe PNAV score is an objective and easy approach to predict the risk of new AVCFs.« less

Osteoporosis

MedlinePlus

... to restore the height of the vertebrae) Spinal fusion (bones of your spine are joined together so ... osteoporosis Patient Instructions Hip fracture - discharge Preventing falls Images Compression fracture Bone density scan Osteoporosis Osteoporosis Hip ...

Vertebral Compression Fractures

MedlinePlus

... and monitored to avoid putting pressure on the ribs that can cause new fractures. Surgical Procedures • When there is severe incapacitating pain • When healing is delayed or when bone fragments ...

Use of intramedullary fibular strut graft: a novel adjunct to plating in the treatment of osteoporotic humeral shaft nonunion

PubMed Central

Vamsi, K.; Rao, Sharath K.; Gnanadoss, James J.; Pandian, S.

2008-01-01

Humeral shaft fractures respond well to conservative treatment and unite without much problem. Since it is uncommon, there is not much discussion regarding the management of nonunion in the literature, and hence this is a challenge to the treating orthopaedic surgeon. Osteoporosis of the fractured bone and stiffness of the surrounding joints compounds the situation further. The Ilizarov fixator, locking compression plate, and vascularised fibular graft are viable options in this scenario but are technically demanding. We used a fibular strut graft for bridging the fracture site in order to enhance the pull-out strength of the screws of the dynamic compression plate. Six patients in the study had successful uneventful union of the fracture at the last follow-up. The fibula is easy to harvest and produces less graft site morbidity. None of the study patients needed additional iliac crest bone grafting. This is the largest reported series of patients with osteoporotic atrophic nonunion of humerus successfully treated solely using the combination of an intramedullary fibular strut graft and dynamic compression plate. PMID:18563410

Direct Observations of Fracture and the Damage Mechanics of Ceramics

DTIC Science & Technology

1988-10-31

microplasticity up to the fracture load. d. It shculd have low enough strength in tension and compression to enable strength measurements at easily accessible...15jm. SEM examination of the grains after large amounts of deformation indicated that the grains are brittle without any evidence of microplasticity . In...and microplasticity in polycrystalline alumina", J.Mater.Sci., 12(1977)791-796. 93. J Lankford, "Compressive microfracture and indentation damage in A1

Synthesis of an Al-Mn-Based Alloy Containing In Situ-Formed Quasicrystals and Evaluation of Its Mechanical and Corrosion Properties

NASA Astrophysics Data System (ADS)

Naglič, Iztok; Samardžija, Zoran; Delijić, Kemal; Kobe, Spomenka; Leskovar, Blaž; Markoli, Boštjan

2018-05-01

An Al-Mn alloy with additions of copper, magnesium, and silicon was prepared and cast into a copper mold. It contains in situ-formed icosahedral quasicrystals (iQCs), as confirmed by electron backscatter diffraction. The aim of this work is to present the mechanical and corrosion properties of this alloy and compare its properties with some conventional commercial materials. The compressive strength and compressive yield strength were 751 MPa and 377 MPa, while the compressive fracture strain was 19%. It was observed that intensive shearing caused the final fracture of the specimens and the fractured iQC dendrites still showed cohesion with the α-Al matrix. The polarization resistance and corrosion rate of the artificially aged alloy were 7.30 kΩ and 1.2 μm/year. The evaluated properties are comparable to conventional, discontinuously reinforced aluminum metal-matrix composites and structural wrought aluminum alloys.

Bonded-cell model for particle fracture.

PubMed

Nguyen, Duc-Hanh; Azéma, Emilien; Sornay, Philippe; Radjai, Farhang

2015-02-01

Particle degradation and fracture play an important role in natural granular flows and in many applications of granular materials. We analyze the fracture properties of two-dimensional disklike particles modeled as aggregates of rigid cells bonded along their sides by a cohesive Mohr-Coulomb law and simulated by the contact dynamics method. We show that the compressive strength scales with tensile strength between cells but depends also on the friction coefficient and a parameter describing cell shape distribution. The statistical scatter of compressive strength is well described by the Weibull distribution function with a shape parameter varying from 6 to 10 depending on cell shape distribution. We show that this distribution may be understood in terms of percolating critical intercellular contacts. We propose a random-walk model of critical contacts that leads to particle size dependence of the compressive strength in good agreement with our simulation data.

[Effect of pneumatic compression in connection with ergotherapeutic treatment of Colles' fracture. A clinical controlled trial].

PubMed

Svensson, B H; Frellsen, M B; Basse, P N; Bliddal, H; Caspers, J; Parby, K

1993-02-15

We followed forty women with functional deficits in the wrist and hand after sustaining a Colles' fracture. The women participated in occupational therapy three times a week for three weeks. At the initial evaluation, after three weeks, and at a three month evaluation, we measured the following: range of joint movement, grip strength, hand volume (oedema), pain and ADL. There was significant improvement in most of the parameters measured after three weeks of occupational therapy, with a less significant improvement from three weeks to three months. Seventeen of the forty women received twenty minutes of intermittent pneumatic compression before occupational therapy. These patients showed significant improvement in wrist extension, compared with the control group of twenty-three patients. Occupational therapy is recommended for patients showing a functional deficit after Colles' fracture. Intermittent pneumatic compression is recommended as a supplement to occupational therapy.

Impact resistance and interlaminar fracture toughness of through-the-thickness reinforced graphite/epoxy

NASA Technical Reports Server (NTRS)

Dexter, H. B.; Funk, J. G.

1986-01-01

Five through-the-thickness stitch configurations are analyzed to determine the effect of impact resistance and interlaminar fracture toughness on T3000/3501-6 graphite/epoxy. The test specimens were stitched with either polyester or Kevlar yarns and with various stitch parameters. Tension and compression mechanical, impact and compression-after-impact, and double cantilever beam tests were conducted. It is observed that the stitched laminates have tension and compression strengths 20-25 percent lower than the strengths of unstitched laminates, the tension strength of stitched laminates is reduced with increasing number of stitches, and the compression strength increases as the number of stitches are increased. The impact data reveal that the Kevlar stitched laminates have less damage than unstitched laminates; the most effective configuration for suppressing impact damage and improving interlaminar fracture toughness consists of Kevlar yarns 1/4 inch apart with eight stitches per inch. The mode 1 critical strain energy release rate for the 1/4 inch Kevlar eight stitch laminate was calculated as 30 times higher than that of the unstitched.

Does plate type influence the clinical outcomes and implant removal in midclavicular fractures fixed with 2.7-mm anteroinferior plates? A retrospective cohort study

PubMed Central

2014-01-01

Background The purpose of this study was to evaluate surgical healing rates, implant failure, implant removal, and the need for surgical revision with regards to plate type in midshaft clavicle fractures fixed with 2.7-mm anteroinferior plates utilizing modern plating techniques. Methods This retrospective exploratory cohort review took place at a level I teaching trauma center and a single large private practice office. A total of 155 skeletally mature individuals with 156 midshaft clavicle fractures between March 2002 and March 2012 were included in the final results. Fractures were identified by mechanism of injury and classified based on OTA/AO criteria. All fractures were fixed with 2.7-mm anteroinferior plates. Primary outcome measurements included implant failure, malunion, nonunion, and implant removal. Secondary outcome measurements included pain with the visual analog scale and range of motion. Statistically significant testing was set at 0.05, and testing was performed using chi-square, Fisher’s exact, Mann–Whitney U, and Kruskall-Wallis. Results Implant failure occurred more often in reconstruction plates as compared to dynamic compression plates (p = 0.029). Malunions and nonunions occurred more often in fractures fixed with reconstruction plates as compared to dynamic compression plates, but it was not statistically significant. Implant removal attributed to irritation or implant prominence was observed in 14 patients. Statistically significant levels of pain were seen in patients requiring implant removal (p = 0.001) but were not associated with the plate type. Conclusions Anteroinferior clavicular fracture fixation with 2.7-mm dynamic compression plates results in excellent healing rates with low removal rates in accordance with the published literature. Given higher rates of failure, 2.7-mm reconstruction plates should be discouraged in comparison to stiffer and more reliable 2.7-mm dynamic compression plates. PMID:24993508

[APPLICATION OF COMPRESSION MINI-SCREWS IN TREATMENT OF PATIENTS WITH INJURY OF ELBOW JOINT BONES].

PubMed

Neverov, V A; Egorov, K S

2015-01-01

A case report presents the experience of application of compression pileateless mini-screws (Gerbert's screws) in treatment of intra-articular fractures, which formed the elbow joint (44 cases). There were performed 32 operations concerning fracture of head of radius, 10 operations on the occasion of fractures of distal section of the humerus and 2 operations on the coronoid process. Long-term treatment results were followed-up in 31 patients during more than 6 months. On basis of analysis of treatment results the authors made a conclusion that the application of mini-screws in case of bone fractures, which formed the elbow joint, allowed realization of stable osteosynthesis after anatomic reposition of articular surfaces, obtaining good anatomical and functional result and shortened the terms of patient's treatment.

Fixation of osteoporotic fractures in the upper limb with a locking compression plate.

PubMed

Neuhaus, V; King, J D; Jupiter, J B

2012-01-01

Locking Compression Plate (LCP) has the advantageous feature that screws can be locked in the plate leaving an angular stable construct. There is no need to have contact between the plate and the bone to achieve stability resulting from friction of the plate-bone-construct. Therefore the plate does not need to be contoured exactly to the bone and the healing bone's periosteal blood supply is not affected. The LCP is used as a bridging plate to gain relative stability in multi-fragmentary, diaphyseal or metaphyseal fractures. Depending on the fracture, the combination hole can also allow the LCP to achieve absolute stability similar to conventional fixation techniques. Osteoporotic fractures have significant impact on morbidity and mortality. Proximal humeral and distal radius fractures are typical examples. These osteoporotic and often comminuted fractures are ideal settings/indications for LCP utilization in the upper extremity. However, the data quality is due to mostly small study populations not so powerful. Unquestionably there has been a clear and fashionable trend to choose operative treatment for these fractures, because the angular stability allows stable fixation and early functional mobilization.

Finite element modeling as a tool for predicting the fracture behavior of robocast scaffolds.

PubMed

Miranda, Pedro; Pajares, Antonia; Guiberteau, Fernando

2008-11-01

The use of finite element modeling to calculate the stress fields in complex scaffold structures and thus predict their mechanical behavior during service (e.g., as load-bearing bone implants) is evaluated. The method is applied to identifying the fracture modes and estimating the strength of robocast hydroxyapatite and beta-tricalcium phosphate scaffolds, consisting of a three-dimensional lattice of interpenetrating rods. The calculations are performed for three testing configurations: compression, tension and shear. Different testing orientations relative to the calcium phosphate rods are considered for each configuration. The predictions for the compressive configurations are compared to experimental data from uniaxial compression tests.

On optimization of a composite bone plate using the selective stress shielding approach.

PubMed

Samiezadeh, Saeid; Tavakkoli Avval, Pouria; Fawaz, Zouheir; Bougherara, Habiba

2015-02-01

Bone fracture plates are used to stabilize fractures while allowing for adequate compressive force on the fracture ends. Yet the high stiffness of conventional bone plates significantly reduces compression at the fracture site, and can lead to subsequent bone loss upon healing. Fibre-reinforced composite bone plates have been introduced to address this drawback. However, no studies have optimized their configurations to fulfill the requirements of proper healing. In the present study, classical laminate theory and the finite element method were employed for optimization of a composite bone plate. A hybrid composite made of carbon fibre/epoxy with a flax/epoxy core, which was introduced previously, was optimized by varying the laminate stacking sequence and the contribution of each material, in order to minimize the axial stiffness and maximize the torsional stiffness for a given range of bending stiffness. The initial 14×4(14) possible configurations were reduced to 13 after applying various design criteria. A comprehensive finite element model, validated against a previous experimental study, was used to evaluate the mechanical performance of each composite configuration in terms of its fracture stability, load sharing, and strength in transverse and oblique Vancouver B1 fracture configurations at immediately post-operative, post-operative, and healed bone stages. It was found that a carbon fibre/epoxy plate with an axial stiffness of 4.6 MN, and bending and torsional stiffness of 13 and 14 N·m(2), respectively, showed an overall superiority compared with other laminate configurations. It increased the compressive force at the fracture site up to 14% when compared to a conventional metallic plate, and maintained fracture stability by ensuring the fracture fragments' relative motions were comparable to those found during metallic plate fixation. The healed stage results revealed that implantation of the titanium plate caused a 40.3% reduction in bone stiffness, while the composite plate lowered the stiffness by 32.9% as compared to the intact femur. This study proposed a number of guidelines for the design of composite bone plates. The findings suggest that a composite bone plate could be customized to allow for moderate compressive force on the fracture ends, while remaining relatively rigid in bending and torsion and strong enough to withstand external loads when a fracture gap is present. The results indicate that the proposed composite bone plate could be a potential candidate for bone fracture plate applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

Vertebral Augmentation Involving Vertebroplasty or Kyphoplasty for Cancer-Related Vertebral Compression Fractures: An Economic Analysis

PubMed Central

2016-01-01

Background Untreated vertebral compression fractures can have serious clinical consequences and impose a considerable impact on patients' quality of life and on caregivers. Since non-surgical management of these fractures has limited effectiveness, vertebral augmentation procedures are gaining acceptance in clinical practice for pain control and fracture stabilization. The objective of this analysis was to determine the cost-effectiveness and budgetary impact of kyphoplasty or vertebroplasty compared with non-surgical management for the treatment of vertebral compression fractures in patients with cancer. Methods We performed a systematic review of health economic studies to identify relevant studies that compare the cost-effectiveness of kyphoplasty or vertebroplasty with non-surgical management for the treatment of vertebral compression fractures in adults with cancer. We also performed a primary cost-effectiveness analysis to assess the clinical benefits and costs of kyphoplasty or vertebroplasty compared with non-surgical management in the same population. We developed a Markov model to forecast benefits and harms of treatments, and corresponding quality-adjusted life years and costs. Clinical data and utility data were derived from published sources, while costing data were derived using Ontario administrative sources. We performed sensitivity analyses to examine the robustness of the results. In addition, a 1-year budget impact analysis was performed using data from Ontario administrative sources. Two scenarios were explored: (a) an increase in the total number of vertebral augmentation procedures performed among patients with cancer in Ontario, maintaining the current proportion of kyphoplasty versus vertebroplasty; and (b) no increase in the total number of vertebral augmentation procedures performed among patients with cancer in Ontario but an increase in the proportion of kyphoplasties versus vertebroplasties. Results The base case considered each of kyphoplasty and vertebroplasty versus non-surgical management. Kyphoplasty and vertebroplasty were associated with an incremental cost-effectiveness ratio of $33,471 and $17,870, respectively, per quality-adjusted life-year gained. The budgetary impact of funding vertebral augmentation procedures for the treatment of vertebral compression fractures in adults with cancer in Ontario was estimated at about $2.5 million in fiscal year 2014/15. More widespread use of vertebral augmentation procedures raised total expenditures under a number of scenarios, with costs increasing by $67,302 to $913,386. Conclusions Our findings suggest that the use of kyphoplasty or vertebroplasty in the management of vertebral compression fractures in patients with cancer may be a cost-effective strategy at commonly accepted willingness-to-pay thresholds. Nonetheless, more widespread use of kyphoplasty (and vertebroplasty to a lesser extent) would likely be associated with net increases in health care costs. PMID:27293494

Innovations in the management of hip fractures.

PubMed

Teasdall, Robert D; Webb, Lawrence X

2003-08-01

Hip fractures include fractures of the head, neck, intertrochanteric, and subtrochanteric regions. Head fractures commonly accompany dislocations. Neck fractures and intertrochanteric fractures occur with greatest frequency in elderly patients with a low bone mineral density and are produced by low-energy mechanisms. Subtrochanteric fractures occur in a predominantly strong cortical osseous region that is exposed to large compressive stresses. Implants used to address these fractures must accommodate significant loads while the fractures consolidate. Complications secondary to hip fractures produce significant morbidity and include infection, nonunion, malunion, decubitus ulcers, fat emboli, deep venous thrombosis, pulmonary embolus, pneumonia, myocardial infarction, stroke, and death.

CT incidence of Morel-Lavallee lesions in patients with pelvic fractures: a 4-year experience at a level 1 trauma center.

PubMed

Beckmann, Nicholas M; Cai, Chunyan

2016-12-01

The aim of this study is to determine the incidence and location of Morel-Lavallee lesions (MLLs) on pelvic CTs performed in evaluation of pelvic fractures and determine if correlation exists between MLLs and mechanism of injury or pelvic ring injury pattern. A retrospective review was performed of pelvic CTs on 1493 consecutive patients presenting with pelvic fractures at our level 1 trauma center. MLLs occurred in 182 of 1493 patients presenting with pelvic fractures. Statistical significance in MLL incidence was found across mechanism of injuries with MLLs being seen most frequently in MCC/ATV accidents and crush injuries. A little over half of MLLs occurred over the lateral thigh with almost all other MLLs occurring over the posterior (flank or lumbar) region. MLLs were much more common in vertical shear and spinopelvic dissociation pelvic ring fracture patterns compared to lateral compression and AP compression patterns. In lateral compression injuries, MLLs most commonly occurred over the thigh. In all other pelvic ring injury patterns, MLLs were predominately posterior. MLL's are not as rare as previously believed. The lateral thigh and lumbar/flank regions should be closely inspected on pelvic trauma patients to identify MLLs, particularly in patients with a spinopelvic dissociation injury pattern.

Substantial vertebral body osteophytes protect against severe vertebral fractures in compression

PubMed Central

Aubin, Carl-Éric; Chaumoître, Kathia; Mac-Thiong, Jean-Marc; Ménard, Anne-Laure; Petit, Yvan; Garo, Anaïs; Arnoux, Pierre-Jean

2017-01-01

Recent findings suggest that vertebral osteophytes increase the resistance of the spine to compression. However, the role of vertebral osteophytes on the biomechanical response of the spine under fast dynamic compression, up to failure, is unclear. Seventeen human spine specimens composed of three vertebrae (from T5-T7 to T11-L1) and their surrounding soft tissues were harvested from nine cadavers, aged 77 to 92 years. Specimens were imaged using quantitative computer tomography (QCT) for medical observation, classification of the intervertebral disc degeneration (Thomson grade) and measurement of the vertebral trabecular density (VTD), height and cross-sectional area. Specimens were divided into two groups (with (n = 9) or without (n = 8) substantial vertebral body osteophytes) and compressed axially at a dynamic displacement rate of 1 m/s, up to failure. Normalized force-displacement curves, videos and QCT images allowed characterizing failure parameters (force, displacement and energy at failure) and fracture patterns. Results were analyzed using chi-squared tests for sampling distributions and linear regression for correlations between VTD and failure parameters. Specimens with substantial vertebral body osteophytes present higher stiffness (2.7 times on average) and force at failure (1.8 times on average) than other segments. The presence of osteophytes significantly influences the location, pattern and type of fracture. VTD was a good predictor of the dynamic force and energy at failure for specimens without substantial osteophytes. This study also showed that vertebral body osteophytes provide a protective mechanism to the underlying vertebra against severe compression fractures. PMID:29065144

Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

DOE PAGES

Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; ...

2015-09-22

Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containingmore » numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.« less

Compressive Stress-Induced Microcracks and Effective Elastic Properties of Limestone and Concrete. Phase 1

DTIC Science & Technology

1991-04-19

McLennan (Technical Consultant) Ph.D. Rock Mechanics, University of Toronto, 1980. Thesis Title: " Hydraulic Fracturing : A Fracture Mechanics Approach...the principal stresses. Certain techniques such as micro- hydraulic fracturing , televiewer surveys and mapping of borehole breakouts have been used to

Finite Element Analysis of Foot and Ankle Impact Injury: Risk Evaluation of Calcaneus and Talus Fracture.

PubMed

Wong, Duo Wai-Chi; Niu, Wenxin; Wang, Yan; Zhang, Ming

2016-01-01

Foot and ankle impact injury is common in geriatric trauma and often leads to fracture of rearfoot, including calcaneus and talus. The objective of this study was to assess the influence of foot impact on the risk of calcaneus and talus fracture via finite element analysis. A three-dimensional finite element model of foot and ankle was constructed based on magnetic resonance images of a female aged 28. The foot sustained a 7-kg passive impact through a foot plate. The simulated impact velocities were from 2.0 to 7.0 m/s with 1.0 m/s interval. At 5.0 m/s impact velocity, the maximum von Mises stress of the trabecular calcaneus and talus were 3.21MPa and 2.41MPa respectively, while that of the Tresca stress were 3.46MPa and 2.55MPa. About 94% and 84% of the trabecular calcaneus and talus exceeded the shear yielding stress, while 21.7% and 18.3% yielded the compressive stress. The peak stresses were distributed around the talocalcaneal articulation and the calcaneal tuberosity inferiorly, which corresponded to the common fracture sites. The prediction in this study showed that axial compressive impact at 5.0 m/s could produce considerable yielding of trabecular bone in both calcaneus and talus, dominantly by shear and compounded with compression that predispose the rearfoot in the risk of fracture. This study suggested the injury pattern and fracture mode of high energy trauma that provides insights in injury prevention and fracture management.

Evaluation of an injectable hydrogel and polymethyl methacrylate in restoring mechanics to compressively fractured spine motion segments.

PubMed

Balkovec, Christian; Vernengo, Andrea J; Stevenson, Peter; McGill, Stuart M

2016-11-01

Compressive fracture can produce profound changes to the mechanical profile of a spine segment. Minimally invasive repair has the potential to restore both function and structural integrity to an injured spine. Use of both hydrogels to address changes to the disc, combined with polymethyl methacrylate (PMMA) to address changes to the vertebral body, has the potential to facilitate repair. The purpose of this investigation was to determine if the combined use of hydrogel injection and PMMA could restore the mechanical profile of an axially injured spinal motion segment. This is a basic science study evaluating a combination of hydrogel injection and vertebroplasty on restoring mechanics to compressively injured porcine spine motion segments. Fourteen porcine spine motion segments were subject to axial compression until fracture using a dynamic servohydraulic testing apparatus. Rotational and compressive stiffness was measured for each specimen under the following conditions: initial undamaged, fractured, fatigue loading under compression, hydrogel injection, PMMA injection, and fatigue loading under compression. Group 1 received hydrogel injection followed by PMMA injection, whereas Group 2 received PMMA injection followed by hydrogel injection. This study was funded under a Natural Sciences and Engineering Research Council of Canada discovery grant. PMMA injection was found to alter the compressive stiffness properties of axially injured spine motion segments, restoring values from Groups 1 and 2 to 89.3%±29.3% and 81%±27.9% of initial values respectively. Hydrogel injection was found to alter the rotational stiffness properties, restoring specimens in Groups 1 and 2 to 151.5%±81% and 177.2%±54.9% of initial values respectively. Prolonged restoration of function was not possible, however, after further fatigue loading. Using this repair technique, replication of the mechanism of injury appears to cause a rapid deterioration in function of the motion segments. Containment of the hydrogel appears to be an issue with large breaches in the end plate, as it is posited to migrate into the cancellous bone of the vertebral body. Future work should attempt to evaluate methods in fully sealing the disc space. Copyright © 2016 Elsevier Inc. All rights reserved.

Proximal femoral fractures.

PubMed

Webb, Lawrence X

2002-01-01

Fractures of the proximal femur include fractures of the head, neck, intertrochanteric, and subtrochanteric regions. Head fractures commonly accompany dislocations. Neck fractures and intertrochanteric fractures occur with greatest frequency in elderly patients with a low bone mineral density and are produced by low-energy mechanisms. Subtrochanteric fractures occur in a predominantly strong cortical osseous region which is exposed to large compressive stresses. Implants used to address these fractures must be able to accommodate significant loads while the fractures consolidate. Complications secondary to these injuries produce significant morbidity and include infection, nonunion, malunion, decubitus ulcers, fat emboli, deep venous thrombosis, pulmonary embolus, pneumonia, myocardial infarction, stroke, and death.

Toughness-Dominated Regime of Hydraulic Fracturing in Cohesionless Materials

NASA Astrophysics Data System (ADS)

Germanovich, L. N.; Hurt, R. S.; Ayoub, J.; Norman, W. D.

2011-12-01

This work examines the mechanisms of hydraulic fracturing in cohesionless particulate materials with geotechnical, geological, and petroleum applications. For this purpose, experimental techniques have been developed, and used to quantify the initiation and propagation of hydraulic fractures in saturated particulate materials. The fracturing liquid is injected into particulate materials, which are practically cohesionless. The liquid flow is localized in thin self-propagating crack-like conduits. By analogy we call them 'cracks' or 'hydraulic fractures.' When a fracture propagates in a solid, new surfaces are created by breaking material bonds. Consequently, the material is in tension at the fracture tip. Because the particulate material is already 'fractured,' no new surface is created and no fracturing process per se is involved. Therefore, the conventional fracture mechanics principles cannot be directly applied. Based on the laboratory observations, performed on three particulate materials (Georgia Red Clay, silica flour, and fine sand, and their mixtures), this work offers physical concepts to explain the observed phenomena. The goal is to determine the controlling parameters of fracture behavior and to quantify their effects. An important conclusion of our work is that all parts of the cohesionless particulate material (including the tip zone of hydraulic fracture) are likely to be in compression. The compressive stress state is an important characteristic of hydraulic fracturing in particulate materials with low, or no, cohesion (such as were used in our experiments). At present, two kinematic mechanisms of fracture propagation, consistent with the compressive stress regime, can be offered. The first mechanism is based on shear bands propagating ahead of the tip of an open fracture. The second is based on the tensile strain ahead of the fracture tip and reduction of the effective stresses to zero within the leak-off zone. Scaling indicates that in our experiments, there is a high pressure gradient in the leak-off zone in the direction normal to the fracture. Fluid pressure does not decrease considerably along the fracture, however, due to the relatively wide fracture aperture. This suggests that hydraulically induced fractures in unconsolidated materials may be considered to be within the toughness-dominated regime of hydraulic fracturing. Our results indicate that the primary influence on peak or initiation pressure comes from the remote stresses. However, fracture morphology changes significantly with other chosen parameters (stress, flow rate, rheology and permeability). Additionally, an important characteristic feature of fractures in our experiments is the frequent bluntness of the fracture tip, which suggests that plastic deformation at the fracture tip is important. Modeling shows that large openings at the fracture tip correspond to relatively large 'effective' fracture (surface) energy, which can be orders of magnitude greater than for typical (solid) rocks.

Whole-body low-dose computed tomography in multiple myeloma staging: Superior diagnostic performance in the detection of bone lesions, vertebral compression fractures, rib fractures and extraskeletal findings compared to radiography with similar radiation exposure.

PubMed

Lambert, Lukas; Ourednicek, Petr; Meckova, Zuzana; Gavelli, Giampaolo; Straub, Jan; Spicka, Ivan

2017-04-01

The primary objective of the present prospective study was to compare the diagnostic performance of conventional radiography (CR) and whole-body low-dose computed tomography (WBLDCT) with a comparable radiation dose reconstructed using hybrid iterative reconstruction technique, in terms of the detection of bone lesions, skeletal fractures, vertebral compressions and extraskeletal findings. The secondary objective was to evaluate lesion attenuation in relation to its size. A total of 74 patients underwent same-day skeletal survey by CR and WBLDCT. In CR and WBLDCT, two readers assessed the number of osteolytic lesions at each region and stage according to the International Myeloma Working Group (IMWG) criteria. A single reader additionally assessed extraskeletal findings and their significance, the number of vertebral compressions and bone fractures. The radiation exposure was 2.7±0.9 mSv for WBLDCT and 2.5±0.9 mSv for CR (P=0.054). CR detected bone involvement in 127 out of 486 regions (26%; P<0.0001), confirmed by WBLDCT. CR underestimated the disease stage in 16% and overestimated it in 8% of the patients (P=0.0077). WBLDCT detected more rib fractures compared with CR (188 vs. 47; P<0.0001), vertebral compressions (93 vs. 67; P=0.010) and extraskeletal findings (194 vs. 52; P<0.0001). There was no correlation observed between lesion size (≥5 mm) and its attenuation (r=-0.006; P=0.93). The inter-observer agreement for the presence of osteolytic lesions was κ=0.76 for WBLDCT, and κ=0.55 for CR. The present study concluded that WBLDCT with hybrid iterative reconstruction technique demonstrates superiority to CR with an identical radiation dose in the detection of bone lesions, skeletal fractures, vertebral compressions and extraskeletal findings, which results in up- or downstaging in 24% patients according to the IMWG criteria. The attenuation of osteolytic lesions can be measured with the avoidance of the partial volume effect.

Using side-opening injection cannulas to prevent cement leakage in percutaneous vertebroplasty for osteoporotic vertebral compression fractures, does it really work?

PubMed

Li, Jigang; Li, Tao; Ma, Qiuhong; Li, Jianmin

2017-09-01

Percutaneous vertebroplasty has been widely applied in the treatment of osteoporotic vertebral compression fractures over the past two decades. However as one of the major complications, the rate of cement leakage seems not to be decreased significantly. In this study, the rate of cement leakage was compared between two groups using two different cement injection cannulas. The purpose was to determine the efficacy of side-opening cannula on preventing cement leakage in vertebroplasty for the treatment of osteoporotic vertebral compression fractures. A retrospective study was conducted from January 2013 to December 2015. Totally 225 patients who received bilateral vertebroplasty due to osteoporotic vertebral compression fractures were included in the study. The patients were divided into test group who received vertebroplasty with side-opening cannulas and control group who received vertebroplasty with front-opening cannulas. The patients' medical records were reviewed to determine the bone marrow density, preoperative vertebral compression ratio, preoperative and postoperative VAS, operation time, volume of injected bone cement, rate of cement leakage. Post-operative X-rays and CT scans were utilized to assess the degree of Cement leakage. Comparisons between groups and clinical results on VAS in each group were analyzed with appropriate test. All the patients were performed successfully without symptomatic complications. The back pain was significantly relieved after operation in both groups (P < 0.05). At 6 days and 6 months follow-up, there was no significant difference in the mean VAS score between the two groups (P > 0.05). The rate of cement leakage in the test group was significantly lower than that in the control group (P < 0.05). Percutaneous vertebroplasty with side-opening cannula is a safe and effective minimally invasive method in the treatment of osteoporotic vertebral compression fractures, the rate of cement leakage can be significantly reduced by redirecting the cement flow. Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

Vertebral Augmentation Involving Vertebroplasty or Kyphoplasty for Cancer-Related Vertebral Compression Fractures: A Systematic Review

PubMed Central

Pron, Gaylene; Holubowich, Corinne; Kaulback, Kellee

2016-01-01

Background Cancers that metastasize to the spine and primary cancers such as multiple myeloma can result in vertebral compression fractures or instability. Conservative strategies, including bed rest, bracing, and analgesic use, can be ineffective, resulting in continued pain and progressive functional disability limiting mobility and self-care. Surgery is not usually an option for cancer patients in advanced disease states because of their poor medical health or functional status and limited life expectancy. The objectives of this review were to evaluate the effectiveness and safety of percutaneous image-guided vertebral augmentation techniques, vertebroplasty and kyphoplasty, for palliation of cancer-related vertebral compression fractures. Methods We performed a systematic literature search for studies on vertebral augmentation of cancer-related vertebral compression fractures published from January 1, 2000, to October 2014; abstracts were screened by a single reviewer. For those studies meeting the eligibility criteria, full-text articles were obtained. Owing to the heterogeneity of the clinical reports, we performed a narrative synthesis based on an analytical framework constructed for the type of cancer-related vertebral fractures and the diversity of the vertebral augmentation interventions. Results The evidence review identified 3,391 citations, of which 111 clinical reports (4,235 patients) evaluated the effectiveness of vertebroplasty (78 reports, 2,545 patients) or kyphoplasty (33 reports, 1,690 patients) for patients with mixed primary spinal metastatic cancers, multiple myeloma, or hemangiomas. Overall the mean pain intensity scores often reported within 48 hours of vertebral augmentation (kyphoplasty or vertebroplasty), were significantly reduced. Analgesic use, although variably reported, usually involved parallel decreases, particularly in opioids, and mean pain-related disability scores were also significantly improved. In a randomized controlled trial comparing kyphoplasty with usual care, improvements in pain scores, pain-related disability, and health-related quality of life were significantly better in the kyphoplasty group than in the usual care group. Bone cement leakage, mostly asymptomatic, was commonly reported after vertebroplasty and kyphoplasty. Major adverse events, however, were uncommon. Conclusions Both vertebroplasty and kyphoplasty significantly and rapidly reduced pain intensity in cancer patients with vertebral compression fractures. The procedures also significantly decreased the need for opioid pain medication, and functional disabilities related to back and neck pain. Pain palliative improvements and low complication rates were consistent across the various cancer populations and vertebral fractures that were investigated. PMID:27298655

Vertebral Augmentation Involving Vertebroplasty or Kyphoplasty for Cancer-Related Vertebral Compression Fractures: A Systematic Review.

PubMed

2016-01-01

Cancers that metastasize to the spine and primary cancers such as multiple myeloma can result in vertebral compression fractures or instability. Conservative strategies, including bed rest, bracing, and analgesic use, can be ineffective, resulting in continued pain and progressive functional disability limiting mobility and self-care. Surgery is not usually an option for cancer patients in advanced disease states because of their poor medical health or functional status and limited life expectancy. The objectives of this review were to evaluate the effectiveness and safety of percutaneous image-guided vertebral augmentation techniques, vertebroplasty and kyphoplasty, for palliation of cancer-related vertebral compression fractures. We performed a systematic literature search for studies on vertebral augmentation of cancer-related vertebral compression fractures published from January 1, 2000, to October 2014; abstracts were screened by a single reviewer. For those studies meeting the eligibility criteria, full-text articles were obtained. Owing to the heterogeneity of the clinical reports, we performed a narrative synthesis based on an analytical framework constructed for the type of cancer-related vertebral fractures and the diversity of the vertebral augmentation interventions. The evidence review identified 3,391 citations, of which 111 clinical reports (4,235 patients) evaluated the effectiveness of vertebroplasty (78 reports, 2,545 patients) or kyphoplasty (33 reports, 1,690 patients) for patients with mixed primary spinal metastatic cancers, multiple myeloma, or hemangiomas. Overall the mean pain intensity scores often reported within 48 hours of vertebral augmentation (kyphoplasty or vertebroplasty), were significantly reduced. Analgesic use, although variably reported, usually involved parallel decreases, particularly in opioids, and mean pain-related disability scores were also significantly improved. In a randomized controlled trial comparing kyphoplasty with usual care, improvements in pain scores, pain-related disability, and health-related quality of life were significantly better in the kyphoplasty group than in the usual care group. Bone cement leakage, mostly asymptomatic, was commonly reported after vertebroplasty and kyphoplasty. Major adverse events, however, were uncommon. Both vertebroplasty and kyphoplasty significantly and rapidly reduced pain intensity in cancer patients with vertebral compression fractures. The procedures also significantly decreased the need for opioid pain medication, and functional disabilities related to back and neck pain. Pain palliative improvements and low complication rates were consistent across the various cancer populations and vertebral fractures that were investigated.

A Clinically Realistic Large Animal Model of Intra-Articular Fracture

DTIC Science & Technology

2012-10-01

articular bone intact. The distal impact face is anchored to the talus using three “tripod” pins, for direct (i.e., no soft tissue intervention) delivery of...pilon) fractures. In this technique, the porcine hock joint (human ankle analogue) is subjected to an injurious transarticular compressive force pulse...fracture, to create fractures morphologically similar to human ankle anterior malleolar fractures. This cut was made on the anterior distal tibial cortex

Cost-Effectiveness Analysis of Percutaneous Vertebroplasty for Osteoporotic Compression Fractures.

PubMed

Takura, Tomoyuki; Yoshimatsu, Misako; Sugimori, Hiroki; Takizawa, Kenji; Furumatsu, Yoshiyuki; Ikeda, Hirotaka; Kato, Hiroshi; Ogawa, Yukihisa; Hamaguchi, Shingo; Fujikawa, Atsuko; Satoh, Toshihiko; Nakajima, Yasuo

2017-04-01

Single-center, single-arm, prospective time-series study. To assess the cost-effectiveness and improvement in quality of life (QOL) of percutaneous vertebroplasty (PVP). PVP is known to relieve back pain and increase QOL for osteoporotic compression fractures. However, the economic value of PVP has never been evaluated in Japan where universal health care system is adopted. We prospectively followed up 163 patients with acute vertebral osteoporotic compression fractures, 44 males aged 76.4±6.0 years and 119 females aged 76.8±7.1 years, who underwent PVP. To measure health-related QOL and pain during 52 weeks observation, we used the European Quality of Life-5 Dimensions (EQ-5D), the Rolland-Morris Disability Questionnaire (RMD), the 8-item Short-Form health survey (SF-8), and visual analogue scale (VAS). Quality-adjusted life years (QALY) were calculated using the change of health utility of EQ-5D. The direct medical cost was calculated by accounting system of the hospital and Japanese health insurance system. Cost-effectiveness was analyzed using incremental cost-effectiveness ratio (ICER): Δ medical cost/Δ QALY. After PVP, improvement in EQ-5D, RMD, SF-8, and VAS scores were observed. The gain of QALY until 52 weeks was 0.162. The estimated lifetime gain of QALY reached 1.421. The direct medical cost for PVP was ¥286,740 (about 3061 US dollars). Cost-effectiveness analysis using ICER showed that lifetime medical cost for a gain of 1 QALY was ¥201,748 (about 2154 US dollars). Correlations between changes in EQ-5D scores and other parameters such as RMD, SF-8, and VAS were observed during most of the study period, which might support the reliability and applicability to measure health utilities by EQ-5D for osteoporotic compression fractures in Japan as well. PVP may improve QOL and ameliorate pain for acute osteoporotic compression fractures and be cost-effective in Japan.

Dorsal Plating of Unstable Scaphoid Fractures and Nonunions.

PubMed

Bain, Gregory I; Turow, Arthur; Phadnis, Joideep

2015-09-01

Achieving stable fixation of displaced acute and chronic nonunited scaphoid fractures continues to be a challenge for the treating surgeon. The threaded compression screw has been the mainstay of treatment of these fractures for the last 3 decades; however, persistent nonunion after screw fixation has prompted development of new techniques. Recent results of volar buttress plating have been promising. We describe a novel technique of dorsal scaphoid plating. In contrast to volar plating, the dorsal plate is biomechanically more favorable as it utilizes the tension side of the scaphoid bone for dynamic compression. Dorsal scaphoid plating provides a more stable construct than the traditional Herbert screw and mitigates the need for vascular or corticocancellous bone grafting in most cases.

Comparative study on the treatment of raw and biologically treated textile effluents through submerged nanofiltration.

PubMed

Chen, Qing; Yang, Ying; Zhou, Mengsi; Liu, Meihong; Yu, Sanchuan; Gao, Congjie

2015-03-02

Raw and biologically treated textile effluents were submerged filtrated using lab-fabricated hollow fiber nanofiltration membrane with a molecular weight cut-off of about 650 g/mol. Permeate flux, chemical oxygen demand (COD) reduction, color removal, membrane fouling, and cleaning were investigated and compared by varying the trans-membrane pressure (TMP) and volume concentrating factor (VCF). It was found that both raw and biologically treated textile effluents could be efficiently treated through submerged nanofiltration. The increase of TMP resulted in a decline in water permeability, COD reduction, color removal, and flux recovery ratio, while the increase of VCF resulted in both increased COD reduction and color removal. Under the TMP of 0.4 bar and VCF of 5.0, fluxes of 1.96 and 2.59 l/m(2)h, COD reductions of 95.7 and 94.2%, color removals of 99.0, and 97.3% and flux recovery ratios of 91.1 and 92.9% could be obtained in filtration of raw and biologically treated effluents, respectively. After filtration, the COD and color contents of the raw effluent declined sharply from 1780 to 325 mg/l and 1.200 to 0.060 Abs/cm, respectively, while for the biologically treated effluent, they decreased from 780 to 180 mg/l and 0.370 to 0.045 Abs/cm, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

[Pediatric orbital emphysema caused by a compressed-air pistol shot: a case report].

PubMed

Navarro-Mingorance, A; Reyes-Dominguez, S B; León-León, M C

2014-09-01

We report the case of a 2 year-old child with orbital emphysema secondary to a compressed-air gun shot in the malar region, with no evidence of orbital wall fracture. Conservative treatment was applied, and no complications were observed. Orbital emphysema in the absence of an orbital wall fracture is a rare situation. Orbital emphysema is usually seen in facial trauma associated with damage to the adjacent paranasal sinuses or facial bones. To our knowledge there have been very few reports of orbital emphysema caused by a compressed-air injury. Copyright © 2012 Sociedad Española de Oftalmología. Published by Elsevier Espana. All rights reserved.

Spermicide

MedlinePlus

... come in several different forms: cream, gel, foam, film, and suppositories. Most spermicides contain nonoxynol-9, a ... applicator. Other types of spermicides include vaginal contraceptive film (VCF), a thin sheet placed in the back ...

Pinhole collimator scintigraphy in differential diagnosis of metastasis, fracture, and infections of the spine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahk, Y.W.; Kim, O.H.; Chung, S.K.

1987-04-01

The informational gains obtained by the use of pinhole collimator scintigraphy (PCS) have been well documented. The present study has been undertaken to prospectively investigate its efficacy in diagnosing several commonly occurring spinal diseases. Patient material consisted of metastatic cancer (39 vertebrae), compression fractures (33 vertebrae), tuberculous spondylitis (17 vertebrae), and pyogenic spondylitis (six vertebrae). PCS findings were characterized in terms of localization, appearance, and homogeneity of abnormal radionuclide accumulation. Thus, metastatic cancer manifested as diffusely or focally homogeneous accumulation within the vertebral body or as a typical short-segmental accumulation along the end-plate, whereas compression fracture manifested as characteristic board-likemore » accumulation along the entire length of end-plates. Tuberculous spondylitis, on the other hand, revealed homogeneous accumulation throughout the vertebral body, and pyogenic spondylitis revealed accumulation at the end-zone of opposing vertebral bodies giving sandwich-like appearance. The disk space at the affected level was not narrowed in the former two diseases but it was narrowed in the latter two. It was concluded that PCS may be useful in differentiating metastatic cancer, compression fracture, tuberculous spondylitis, and pyogenic spondylitis.« less

Use of locking compression plates in ulnar fractures of 18 horses.

PubMed

Jacobs, Carrie C; Levine, David G; Richardson, Dean W

2017-02-01

To describe the outcome, clinical findings, and complications associated with the use of the locking compression plate (LCP) for various types of ulnar fractures in horses. Retrospective case series. Client owned horses (n = 18). Medical records, radiographs, and follow-up for horses having an ulnar fracture repaired using at least 1 LCP were reviewed. Fifteen of 18 horses had fractures of the ulna only, and 3 horses had fractures of the ulna and proximal radius. All 18 horses were discharged from the hospital. Complications occurred in 5 horses; incisional infection (n = 4, 22%), implant-associated infection (n = 2, 11%), and colic (n = 1, 6%). Follow-up was available for all horses at a range of 13-120 months and 15 horses (83%) were sound for their intended purpose and 3 horses (17%) were euthanatized. One horse was euthanatized for complications associated with original injury and surgery. The LCP is a viable method of internal fixation for various types of ulnar fractures, with most horses in this series returning to soundness. © 2017 The American College of Veterinary Surgeons.

Treatment of close-range, low-velocity gunshot fractures of tibia and femur diaphysis with consecutive compression-distraction technique: a report of 11 cases.

PubMed

Ateşalp, A Sabri; Kömürcü, Mahmut; Demiralp, Bahtiyar; Bek, Dogan; Oğuz, Erbil; Yanmiş, Ibrahim

2004-01-01

Lower extremity injuries secondary to close-range, low-velocity gunshot wounds are frequently seen in both civilian and military populations. A close-range, low-velocity injury produces high energy and often results in comminuted and complicated fractures with significant morbidity. In this study, four femoral, four tibial, and three combined tibia and fibular comminuted diaphyseal fractures secondary to close-range, low-velocity gunshot wounds in 11 military personnel were treated with debridement followed by compression-distraction lengthening using a circular external fixator frame. Fracture union was obtained in all without significant major complications. Fracture consolidation occurred at a mean of 3.5 months. At follow-up of 46.8 months, there were no delayed unions, nonunions, or malunions. Minor complications included four pin-tract infections and knee flexion limitation in two femur fractures. Osteomyelitis and deep soft tissue infection were not observed. This technique provided an alternative to casting, open reduction internal fixation, or intermedullary fixation with an acceptable complication rate.

Comparative experimental study of dynamic compressive strength of mortar with glass and basalt fibres

NASA Astrophysics Data System (ADS)

Kruszka, Leopold; Moćko, Wojciech; Fenu, Luigi; Cadoni, Ezio

2015-09-01

Specimen reinforced with glass and basalt fibers were prepared using Standard Portland cement (CEM I, 52.5 R as prescribed by EN 197-1) and standard sand, in accordance with EN 196-1. From this cementitious mixture, a reference cement mortar without fibers was first prepared. Compressive strength, modulus of elasticity, and mod of fracture were determined for all specimens. Static and dynamic properties were investigated using Instron testing machine and split Hopkinson pressure bar, respectively. Content of the glass fibers in the mortar does not influence the fracture stress at static loading conditions in a clearly observed way. Moreover at dynamic range 5% content of the fiber results in a significant drop of fracture stress. Analysis of the basalt fibers influence on the fracture stress shows that optimal content of this reinforcement is equal to 3% for both static and dynamic loading conditions. Further increase of the fiber share gives the opposite effect, i.e. drop of the fracture stress.

The effect of luting media on the fracture resistance of a flame sprayed all-ceramic crown.

PubMed

Casson, A M; Glyn Jones, J C; Youngson, C C; Wood, D J

2001-11-01

This in vitro study investigated the effect of selected luting media on the fracture resistance of a flame-sprayed all-ceramic crown. Three groups of 10 human upper premolar teeth were prepared for crowning using a standardised technique. Flame sprayed crowns were fabricated and cemented onto the preparations using zinc phosphate (ZPC), glass polyalkenoate (GPC) or composite luting cement (CLC). During crown seating, a pressure perfusion system simulated pulpal fluid outflow equivalent to 300mm of H2O. Compressive fracture resistance was determined for each group using a Universal Testing Machine with a crosshead speed of 1mm min(-1). A group of unrestored teeth acted as a control. The fracture resistance of the groups ranked as follows: ZPC>CLC>GPC=unrestored teeth. The difference between the fracture resistance of ZPC and CLC groups and the control group was statistically significant. The mode of fracture between the luted crowns and natural crowns was markedly different. When tested in compression, a new, flame-sprayed all-ceramic crown, when luted in place using ZPC, GPC or CLC, could produce strengths comparable to or greater than natural unrestored teeth. The luting agent used significantly affected the recorded fracture loads.

Biomechanical outcome of proximal femoral nail antirotation is superior to proximal femoral locking compression plate for reverse oblique intertrochanteric fractures: a biomechanical study of intertrochanteric fractures.

PubMed

Ma, Jian-Xiong; Wang, Jie; Xu, Wei-Guo; Yu, Jing-Tao; Yang, Yang; Ma, Xin-Long

2015-01-01

Reverse obliquity intertrochanteric fractures are a challenge for orthopedic surgeons. The optimal internal fixation for repairing this type of unstable intertrochanteric fractures remains controversial. This study aimed to compare the biomechanical properties in axial load and cyclical axial load of proximal femoral nail antirotation (PFNA) and proximal femoral locking compression plate (PFLCP) for fixation of reverse obliquity intertrochanteric fractures. Sixteen embalmed cadaver femurs were sawed to simulate reverse obliquity intertrochanteric fracture and instrumented with PFNA or PFLCP. Axial loads and axial cyclic loads were applied to the femoral head by an Instron tester. If the implant-femur constructs did not fail, axial failure load was added to the remaining implant-femur constructs. Mean axial stiffness for PFNA was 21.10% greater than that of PFLCP. Cyclic axial loading caused significantly less (p=0.022) mean irreversible deformation in PFNA (3.43 mm) than in PFLCP (4.34 mm). Significantly less (p=0.002) mean total deformation was detected in PFNA (6.16 mm) than in PFLCP (8.67 mm). For fixing reverse obliquity intertrochanteric fractures, PFNA is superior to PFLCP under axial load.

Disadvantages of interfragmentary shear on fracture healing--mechanical insights through numerical simulation.

PubMed

Steiner, Malte; Claes, Lutz; Ignatius, Anita; Simon, Ulrich; Wehner, Tim

2014-07-01

The outcome of secondary fracture healing processes is strongly influenced by interfragmentary motion. Shear movement is assumed to be more disadvantageous than axial movement, however, experimental results are contradictory. Numerical fracture healing models allow simulation of the fracture healing process with variation of single input parameters and under comparable, normalized mechanical conditions. Thus, a comparison of the influence of different loading directions on the healing process is possible. In this study we simulated fracture healing under several axial compressive, and translational and torsional shear movement scenarios, and compared their respective healing times. Therefore, we used a calibrated numerical model for fracture healing in sheep. Numerous variations of movement amplitudes and musculoskeletal loads were simulated for the three loading directions. Our results show that isolated axial compression was more beneficial for the fracture healing success than both isolated shearing conditions for load and displacement magnitudes which were identical as well as physiological different, and even for strain-based normalized comparable conditions. Additionally, torsional shear movements had less impeding effects than translational shear movements. Therefore, our findings suggest that osteosynthesis implants can be optimized, in particular, to limit translational interfragmentary shear under musculoskeletal loading. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Fat embolism syndrome following percutaneous vertebroplasty: a case report.

PubMed

Ahmadzai, Hasib; Campbell, Scott; Archis, Constantine; Clark, William A

2014-04-01

Vertebroplasty is commonly performed for management of pain associated with vertebral compression fractures. There have been two previous reports of fatal fat embolism following vertebroplasty. Here we describe a case of fat embolism syndrome following this procedure, and also provide fluoroscopic video evidence consistent with this occurrence. The purpose of this study was to review the literature and report a case of fat embolism syndrome in a patient who underwent percutaneous vertebroplasty for compression fracture. The study design for this manuscript was of a clinical case report. A 68-year-old woman who developed sudden back pain with minimal trauma was found to have a T6 vertebral compression fracture on radiographs and bone scans. Percutaneous vertebroplasty of T5 and T6 was performed. Fluoroscopic imaging during the procedure demonstrated compression and rarefaction of the fractured vertebra associated with changes in intrathoracic pressure. Immediately after the procedure, the patient's back pain resolved and she was discharged home. Two days later, she developed increasing respiratory distress, confusion, and chest pain. A petechial rash on her upper arms also appeared. No evidence of bone cement leakage or pulmonary filling defects were seen on computed tomography-pulmonary angiography. Brain magnetic resonance imaging demonstrated hyperintensities in the periventricular and subcortical white matter on T2/fluid-attenuated inversion recovery sequences. A diagnosis of fat embolism syndrome was made, and the patient recovered with conservative management. Percutaneous vertebroplasty is a relatively safe and simple procedure, reducing pain and improving functional limitations in patients with vertebral fractures. This case demonstrates an uncommon yet serious complication of fat embolism syndrome. Clinicians must be aware of this complication when explaining the procedure to patients and provide prompt supportive care when it does occur. Copyright © 2014 Elsevier Inc. All rights reserved.

Biomechanical investigation of an alternative concept to angular stable plating using conventional fixation hardware.

PubMed

Windolf, Markus; Klos, Kajetan; Wähnert, Dirk; van der Pol, Bas; Radtke, Roman; Schwieger, Karsten; Jakob, Roland P

2010-05-21

Angle-stable locking plates have improved the surgical management of fractures. However, locking implants are costly and removal can be difficult. The aim of this in vitro study was to evaluate the biomechanical performance of a newly proposed crossed-screw concept ("Fence") utilizing conventional (non-locked) implants in comparison to conventional LC-DCP (limited contact dynamic compression plate) and LCP (locking compression plate) stabilization, in a human cadaveric diaphyseal gap model. In eight pairs of human cadaveric femora, one femur per pair was randomly assigned to receive a Fence construct with either elevated or non-elevated plate, while the contralateral femur received either an LCP or LC-DCP instrumentation. Fracture gap motion and fatigue performance under cyclic loading was evaluated successively in axial compression and in torsion. Results were statistically compared in a pairwise setting. The elevated Fence constructs allowed significantly higher gap motion compared to the LCP instrumentations (axial compression: p

Operative treatment of intra-articular calcaneal fractures with calcaneal plates and its complications

PubMed Central

Rak, Vaclav; Ira, Daniel; Masek, Michal

2009-01-01

Background: In a retrospective study we analysed intra-articular calcaneal fracture treatment by comparing results and complications related to fracture stabilization with nonlocking calcaneal plates and locking compression plates. Materials and Methods: We performed 76 osteosynthesis (67 patients) of intra-articular calcaneal fractures using the standard extended lateral approach from February 2004 to October 2007. Forty-two operations using nonlocking calcaneal plates (group A) were performed during the first three years, and 34 calcaneal fractures were stabilized using locking compression plates (group B) in 2007. In the Sanders type IV fractures, reconstruction of the calcaneal shape was attempted. Depending on the type of late complication, we performed subtalar arthroscopy in six cases, arthroscopically assisted subtalar distraction bone block arthrodesis in six cases, and plate removal with lateral-wall decompression in five cases. The patients were evaluated by the AOFAS Ankle-Hindfoot Scale. Results: Wound healing complications were 7/42 (17%) in group A and 1/34 (3%) in group B. No patient had deep osseous infection or foot rebound compartment syndrome. Preoperative size of Böhler's angle correlated with postoperative clinical results in both groups. There were no late complications necessitating corrective procedure or arthroscopy until December 2008 in Group B. All late complications ccurred in Group A. The overall results according to the AOFAS Ankle Hindfoot Scale were good or excellent in 23/42 (55%) in group A and in 30/34 (85%) in group B. Conclusion: Open reduction and internal fixation of intra-articular calcaneal fractures has become a standard surgical method. Fewer complications and better results related to treatment with locking compression plates confirmed in comparison to nonlocking ones were noted for all Sanders types of intra-articular calcaneal fractures. Age and Sanders type IV fractures are not considered to be the contraindications to surgery. PMID:19838350

Compressive Properties of Metal Matrix Syntactic Foams in Free and Constrained Compression

NASA Astrophysics Data System (ADS)

Orbulov, Imre Norbert; Májlinger, Kornél

2014-06-01

Metal matrix syntactic foam (MMSF) blocks were produced by an inert gas-assisted pressure infiltration technique. MMSFs are advanced hollow sphere reinforced-composite materials having promising application in the fields of aviation, transport, and automotive engineering, as well as in civil engineering. The produced blocks were investigated in free and constrained compression modes, and besides the characteristic mechanical properties, their deformation mechanisms and failure modes were studied. In the tests, the chemical composition of the matrix material, the size of the reinforcing ceramic hollow spheres, the applied heat treatment, and the compression mode were considered as investigation parameters. The monitored mechanical properties were the compressive strength, the fracture strain, the structural stiffness, the fracture energy, and the overall absorbed energy. These characteristics were strongly influenced by the test parameters. By the proper selection of the matrix and the reinforcement and by proper design, the mechanical properties of the MMSFs can be effectively tailored for specific and given applications.

Loading capacity of zirconia implant supported hybrid ceramic crowns.

PubMed

Rohr, Nadja; Coldea, Andrea; Zitzmann, Nicola U; Fischer, Jens

2015-12-01

Recently a polymer infiltrated hybrid ceramic was developed, which is characterized by a low elastic modulus and therefore may be considered as potential material for implant supported single crowns. The purpose of the study was to evaluate the loading capacity of hybrid ceramic single crowns on one-piece zirconia implants with respect to the cement type. Fracture load tests were performed on standardized molar crowns milled from hybrid ceramic or feldspar ceramic, cemented to zirconia implants with either machined or etched intaglio surface using four different resin composite cements. Flexure strength, elastic modulus, indirect tensile strength and compressive strength of the cements were measured. Statistical analysis was performed using two-way ANOVA (p=0.05). The hybrid ceramic exhibited statistically significant higher fracture load values than the feldspar ceramic. Fracture load values and compressive strength values of the respective cements were correlated. Highest fracture load values were achieved with an adhesive cement (1253±148N). Etching of the intaglio surface did not improve the fracture load. Loading capacity of hybrid ceramic single crowns on one-piece zirconia implants is superior to that of feldspar ceramic. To achieve maximal loading capacity for permanent cementation of full-ceramic restorations on zirconia implants, self-adhesive or adhesive cements with a high compressive strength should be used. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Texture Studies and Compression Behaviour of Apple Flesh

NASA Astrophysics Data System (ADS)

James, Bryony; Fonseca, Celia

Compressive behavior of fruit flesh has been studied using mechanical tests and microstructural analysis. Apple flesh from two cultivars (Braeburn and Cox's Orange Pippin) was investigated to represent the extremes in a spectrum of fruit flesh types, hard and juicy (Braeburn) and soft and mealy (Cox's). Force-deformation curves produced during compression of unconstrained discs of apple flesh followed trends predicted from the literature for each of the "juicy" and "mealy" types. The curves display the rupture point and, in some cases, a point of inflection that may be related to the point of incipient juice release. During compression these discs of flesh generally failed along the centre line, perpendicular to the direction of loading, through a barrelling mechanism. Cryo-Scanning Electron Microscopy (cryo-SEM) was used to examine the behavior of the parenchyma cells during fracture and compression using a purpose designed sample holder and compression tester. Fracture behavior reinforced the difference in mechanical properties between crisp and mealy fruit flesh. During compression testing prior to cryo-SEM imaging the apple flesh was constrained perpendicular to the direction of loading. Microstructural analysis suggests that, in this arrangement, the material fails along a compression front ahead of the compressing plate. Failure progresses by whole lines of parenchyma cells collapsing, or rupturing, with juice filling intercellular spaces, before the compression force is transferred to the next row of cells.

Dynamic compressive properties obtained from a split Hopkinson pressure bar test of Boryeong shale

NASA Astrophysics Data System (ADS)

Kang, Minju; Cho, Jung-Woo; Kim, Yang Gon; Park, Jaeyeong; Jeong, Myeong-Sik; Lee, Sunghak

2016-09-01

Dynamic compressive properties of a Boryeong shale were evaluated by using a split Hopkinson pressure bar, and were compared with those of a Hwangdeung granite which is a typical hard rock. The results indicated that the dynamic compressive loading reduced the resistance to fracture. The dynamic compressive strength was lower in the shale than in the granite, and was raised with increasing strain rate by microcracking effect as well as strain rate strengthening effect. Since the number of microcracked fragments increased with increasing strain rate in the shale having laminated weakness planes, the shale showed the better fragmentation performance than the granite at high strain rates. The effect of transversely isotropic plane on compressive strength decreased with increasing strain rate, which was desirable for increasing the fragmentation performance. Thus, the shale can be more reliably applied to industrial areas requiring good fragmentation performance as the striking speed of drilling or hydraulic fracturing machines increased. The present dynamic compressive test effectively evaluated the fragmentation performance as well as compressive strength and strain energy density by controlling the air pressure, and provided an important idea on which rock was more readily fragmented under dynamically processing conditions such as high-speed drilling and blasting.

Improvement of Liquefiable Foundation Conditions Beneath Existing Structures.

DTIC Science & Technology

1985-08-01

filter zones, and drains. Drilling fluids can cause hydraulic fracturing . These hazards can lead to to piping and hvdraulic fracturing Compression . 7...with results of piping and hydraulic fracturing (Continued) * Site conditions have been classified into three cases; Case 1 is for beneath -d...which could lead to piping and hydraulic fracturing Soil Reinforcement 16. Vibro-replacement See methods 2 and 3 stone and sand columns applicable to

Modeling of orthotropic plate fracture under impact load using various strength criteria

NASA Astrophysics Data System (ADS)

Radchenko, Andrey; Krivosheina, Marina; Kobenko, Sergei; Radchenko, Pavel; Grebenyuk, Grigory

2017-01-01

The paper presents the comparative analysis of various tensor multinomial criteria of strength for modeling of orthotropic organic plastic plate fracture under impact load. Ashkenazi, Hoffman and Wu strength criteria were used. They allowed fracture modeling of orthotropic materials with various compressive and tensile strength properties. The modeling of organic plastic fracture was performed numerically within the impact velocity range of 700-1500 m/s.

Redistribution Mechanisms and Quantification of Homogeneity in Friction Stir Welding and Processing of an Aluminum Silicon Alloy

DTIC Science & Technology

2012-09-01

have been extensively studied in regard to the mechanical effects of the Si particle distribution. Micro- mechanisms of fracture are significantly...ratio particles, and that global fracture occurs by linkage of these locally fractured areas. Their overall conclusion was that the mechanical ...interface, which is undergoing deformation in either tension or compression. Particle fracture was found to occur by two mechanisms : interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parab, Niranjan D.; Hudspeth, Matthew; Claus, Ben

Granular materials are widely used to resist impact and blast. Under these dynamic loadings, the constituent particles in the granular system fracture. To study the fracture mechanisms in brittle particles under dynamic compressive loading, a high speed X-ray phase contrast imaging setup was synchronized with a Kolsky bar apparatus. Controlled compressive loading was applied on two contacting particles using the Kolsky bar apparatus and fracture process was captured using the high speed X-ray imaging setup. Five different particles were investigated: soda-lime glass, polycrystalline silica (silicon dioxide), polycrystalline silicon, barium titanate glass, and yttrium stabilized zirconia. For both soda lime glassmore » and polycrystalline silica particles, one of the particles fragmented explosively, thus breaking into many small pieces. For Silicon and barium titanate glass particles, a finite number of cracks were observed in one of the particles causing it to fracture. For yttrium stabilized zirconia particles, a single meridonial crack developed in one of the particles, breaking it into two parts.« less

[Case-control study on minimally invasive percutaneous locking compression plate internal fixation for the treatment of type II and III pilon fractures].

PubMed

Zhang, Zhi-Da; Ye, Xiu-Yi; Shang, Li-Yong; Xu, Rong-Ming; Zhu, Yan-Zhao

2011-12-01

To explore the clinical efficacy of delayed open reduction and internal fixation with minimally invasive percutaneous locking compression plate for the treatment of type II and III Pilon fractures. From January 2007 to September 2009, 32 patients with type II and III Pilon fractures were treated with open reduction and anatomic plate fixation (AP group) and minimally invasive percutaneous locking compression plate osteosynthesis (LCP group). There were 11 males and 6 females in AP group, with an average age of (37.4 +/- 13.3) years (ranged, 19 to 55 years). And there were 10 males and 5 females in LCP group, with an average age of (34.6 +/- 11.3) years(ranged, 21 to 56 years). The operating time, fracture healing time, aligned angulation and ankle function were compared between the two groups. All the patients were followed up, and the during ranged from 12 to 25 months, with a mean of (15.0 +/- 1.7) months. The average operation time was (76.5 +/- 8.3) min for AP group and (58.3 +/- 3.4) min for LCP group; the average time of fracture healing was (20.5 +/- 0.4) weeks for AP group and (15.7 +/- 0.2) weeks for LCP group; the total angulation between anterior posterior film and lateral film was averaged (6.6 +/- 0.5) degrees for AP group and (3.6 +/- 0.2) degrees for LCP group. As to above index, the results of LCP group were better than those of AP group (P < 0.05). According to Kofoed criteria for ankle joint, the results of LCP group were better than those of AP group in ankle joint pain, wakling and ankle joint function (P < 0.05). The method of minimally invasive percutaneous locking compression plate internal fixation is effective in the treatment of Pilon fracture with less invasion, faster bone union, more stabilized fixation, quicker recovery of ankle function and fewer complications, which is more advantaged for type II and III Pilon fractures.

Failure strengths of denture teeth fabricated on injection molded or compression molded denture base resins.

PubMed

Robison, Nathan E; Tantbirojn, Daranee; Versluis, Antheunis; Cagna, David R

2016-08-01

Denture tooth fracture or debonding remains a common problem in removable prosthodontics. The purpose of this in vitro study was to explore factors determining failure strengths for combinations of different denture tooth designs (shape, materials) and injection or compression molded denture base resins. Three central incisor denture tooth designs were tested: nanohybrid composite (NHC; Ivoclar Phonares II), interpenetrating network (IPN; Dentsply Portrait), and microfiller reinforced polyacrylic (MRP; VITA Physiodens). Denture teeth of each type were processed on an injection molded resin (IvoBase HI; Ivoclar Vivadent AG) or a compression molded resin (Lucitone 199; Dentsply Intl) (n=11 or 12). The denture teeth were loaded at 45 degrees on the incisal edge. The failure load was recorded and analyzed with 2-way ANOVA (α=.05), and the fracture mode was categorized from observed fracture surfaces as cohesive, adhesive, or mixed failure. The following failure loads (mean ±SD) were recorded: NHC/injection molded 280 ±52 N; IPN/injection molded 331 ±41 N; MRP/injection molded 247 ±23 N; NHC/compression molded 204 ±31 N; IPN/compression molded 184 ±17 N; MRP/compression molded 201 ±16 N. Injection molded resin yielded significantly higher failure strength for all denture teeth (P<.001), among which IPN had the highest strength. Failure was predominantly cohesive in the teeth, with the exception of mixed mode for the IPN/compression group. When good bonding was achieved, the strength of the structure (denture tooth/base resin combination) was determined by the strength of the denture teeth, which may be affected by the processing technique. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Biomechanical evaluation of a new composite bioresorbable screw.

PubMed

Bailey, C A; Kuiper, J H; Kelly, C P

2006-04-01

A new bioresorbable composite cannulated screw has been developed for small bone fracture fixation. The LG ("Little Grafter") screw is manufactured from Biosteon, which is a composite of poly L-lactic acid and hydroxyapatite. This study aimed to compare interfragmentary compression generated by this new screw with conventional metal screws commonly used in scaphoid fracture fixation. Four small metallic screws were compared with the LG screw, using a bone model produced from rigid polyurethane foam. The screws included the Acutrak, Asnis III, Herbert and Herbert-Whipple screws. The mean maximum compression forces for the LG screw, the Asnis and the Acutrak were comparable (LG 32.3 N, Asnis 32.8 N, Acutrak 38.3 N), whereas those using the Herbert and the Herbert-Whipple screw were significantly lower (Herbert 21.8 N, Herbert-Whipple 19.9 N). The bioresorbable LG screw has been shown to have good compressive properties compared to commonly used small bone fragment compression screws.

A process efficiency assessment of serum protein removal from milk using ceramic graded permeability microfiltration membrane.

PubMed

Tremblay-Marchand, D; Doyen, A; Britten, M; Pouliot, Y

2016-07-01

Microfiltration (MF) is a well-known process that can be used in the dairy industry to separate caseins from serum proteins (SP) in skim milk using membranes with a pore diameter of 0.1μm. Graded permeability ceramic membranes have been studied widely as means of improving milk fractionation by overcoming problems encountered with other MF membranes. The ideal operating parameters for process efficiency in terms of membrane selectivity, permeate flux, casein loss, SP transmission, energy consumption, and dilution with water remain to be determined for this membrane. Our objective was to evaluate the effects of transmembrane pressure (TMP), volumetric concentration factor (VCF), and diafiltration on overall process efficiency. Skim milk was processed using a pilot-scale MF system equipped with 0.72-m(2) graded permeability membranes with a pore size of 0.1μm. In the first experiment, in full recycle mode, TMP was set at 124, 152, 179, or 207 kPa by adjusting the permeate pressure at the outlet. Whereas TMP had no significant effect on permeate and retentate composition, 152 kPa was found to be optimal for SP removal during concentration and concentration or diafiltration experiments. When VCF was increased to 3×, SP rejection coefficient increased along with energy consumption and total casein loss, whereas SP removal rate decreased. Diafiltering twice allowed an increase in total SP removal but resulted in a substantial increase in energy consumption and casein loss. It also reduced the SP removal rate by diluting permeate. The membrane surface area required for producing cheese milk by blending whole milk, cream, and MF retentate (at different VCF) was estimated for different cheese milk casein concentrations. For a given casein concentration, the same quantity of permeate and SP would be produced, but less membrane surface area would be needed at a lower retentate VCF. Microfiltration has great potential as a process of adding value to conventional cheesemaking processes, but its cost-effectiveness at a large scale remains to be demonstrated. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Fracture modes under uniaxial compression in hydroxyapatite scaffolds fabricated by robocasting.

PubMed

Miranda, Pedro; Pajares, Antonia; Saiz, Eduardo; Tomsia, Antoni P; Guiberteau, Fernando

2007-12-01

The fracture modes of hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) are analyzed in this work. Concentrated HA inks with suitable viscoelastic properties were developed to enable the fabrication of prototype structures consisting of a 3-D square mesh of interpenetrating rods. The fracture behavior of these model scaffolds under compressive stresses is determined from in situ uniaxial tests performed in two different directions: perpendicular to the rods and along one of the rod directions. The results are analyzed in terms of the stress field calculated by finite element modeling (FEM). This analysis provides valuable insight into the mechanical behavior of scaffolds for bone tissue engineering applications fabricated by robocasting. Copyright 2007 Wiley Periodicals, Inc.

Transconjunctival orbital emphysema caused by compressed air injury: a case report.

PubMed

Mathew, Sunu; Vasu, Usha; Francis, Febson; Nazareth, Colin

2008-01-01

Orbital emphysema following conjunctival tear in the absence of orbital wall fracture, caused by air under pressure is rare. Usually orbital emphysema is seen in facial trauma associated with damage to the adjacent paranasal sinuses or facial bones. To the best of our knowledge, there have been only eight reports of orbital emphysema following use of compressed air during industrial work. The air under pressure is pushed through the subconjunctival space into the subcutaneous and retrobulbar spaces. We present here a rare cause of orbital emphysema in a young man working with compressed air gun. Although the emphysema was severe, there were no orbital bone fracture and the visual recovery of the patient was complete without attendant complications.

Transconjunctival orbital emphysema caused by compressed air injury: A case report

PubMed Central

Vasu, Usha; Francis, Febson; Nazareth, Colin

2008-01-01

Orbital emphysema following conjunctival tear in the absence of orbital wall fracture, caused by air under pressure is rare. Usually orbital emphysema is seen in facial trauma associated with damage to the adjacent paranasal sinuses or facial bones. To the best of our knowledge, there have been only eight reports of orbital emphysema following use of compressed air during industrial work. The air under pressure is pushed through the subconjunctival space into the subcutaneous and retrobulbar spaces. We present here a rare cause of orbital emphysema in a young man working with compressed air gun. Although the emphysema was severe, there were no orbital bone fracture and the visual recovery of the patient was complete without attendant complications. PMID:18417833

Mechanics of Hydraulic Fractures

NASA Astrophysics Data System (ADS)

Detournay, Emmanuel

2016-01-01

Hydraulic fractures represent a particular class of tensile fractures that propagate in solid media under pre-existing compressive stresses as a result of internal pressurization by an injected viscous fluid. The main application of engineered hydraulic fractures is the stimulation of oil and gas wells to increase production. Several physical processes affect the propagation of these fractures, including the flow of viscous fluid, creation of solid surfaces, and leak-off of fracturing fluid. The interplay and the competition between these processes lead to multiple length scales and timescales in the system, which reveal the shifting influence of the far-field stress, viscous dissipation, fracture energy, and leak-off as the fracture propagates.

Whole Genome Sequence of Two Wild-Derived Mus musculus domesticus Inbred Strains, LEWES/EiJ and ZALENDE/EiJ, with Different Diploid Numbers

PubMed Central

Morgan, Andrew P.; Didion, John P.; Doran, Anthony G.; Holt, James M.; McMillan, Leonard; Keane, Thomas M.; de Villena, Fernando Pardo-Manuel

2016-01-01

Wild-derived mouse inbred strains are becoming increasingly popular for complex traits analysis, evolutionary studies, and systems genetics. Here, we report the whole-genome sequencing of two wild-derived mouse inbred strains, LEWES/EiJ and ZALENDE/EiJ, of Mus musculus domesticus origin. These two inbred strains were selected based on their geographic origin, karyotype, and use in ongoing research. We generated 14× and 18× coverage sequence, respectively, and discovered over 1.1 million novel variants, most of which are private to one of these strains. This report expands the number of wild-derived inbred genomes in the Mus genus from six to eight. The sequence variation can be accessed via an online query tool; variant calls (VCF format) and alignments (BAM format) are available for download from a dedicated ftp site. Finally, the sequencing data have also been stored in a lossless, compressed, and indexed format using the multi-string Burrows-Wheeler transform. All data can be used without restriction. PMID:27765810

Timing of Surgery for Spinal Fractures Associated with Systemic Trauma: A Need for a Strategic and Systemic Approach.

PubMed

Koksal, Ismet; Alagoz, Fatih; Celik, Haydar; Yildirim, Ali Erdem; Akin, Tezcan; Guvenc, Yahya; Karatay, Mete; Erdem, Yavuz

An underestimated evaluation of systemic organs in cases with spinal fractures might jeopardize the intervention for treatment and future complications with an increased morbidity and mortality are almost warranted. In the present study, a retrospective analysis of spinal fracture cases associated with systemic trauma was performed to assess surgical success. A retrospective analysis of patients with thoracolumbar fractures who were admitted to the emergency unit between September 2012 and September 2014 was used for the study. The cases were categorized according to age, sex, reason of trauma, associated trauma, neurological condition and treatment details and results were analysed using SPSS 14.0 for Windows. The most common reason of trauma is detected as falls in 101 cases (64.3%). Radiological evaluation of spinal fractures revealed a compression fracture in 106 cases (67.5%) and other fractures in 51 cases (32.5%). Surgical treatment for spinal fracture was performed in 60.5% of the cases and conservative approach was preferred in 39.5% cases. In non-compressive spinal fractures, an associated pathology like head trauma, lower extremity fracture or neurological deficit was found to be higher in incidence (p < 0.05). Necessity for surgical intervention was found to be more prominent in this group (p < 0.05). However, the fracture type was not found to be associated with morbidity and mortality (p < 0.05). A surgical intervention for a spinal fracture necessitating surgery should rather be performed right after stabilization of the systemic condition which might be associated with decreased morbidity and mortality.

An Experimental Investigation into Failure and Localization Phenomena in the Extension to Shear Fracture Transition in Rock

NASA Astrophysics Data System (ADS)

Choens, R. C., II; Chester, F. M.; Bauer, S. J.; Flint, G. M.

2014-12-01

Fluid-pressure assisted fracturing can produce mesh and other large, interconnected and complex networks consisting of both extension and shear fractures in various metamorphic, magmatic and tectonic systems. Presently, rock failure criteria for tensile and low-mean compressive stress conditions is poorly defined, although there is accumulating evidence that the transition from extension to shear fracture with increasing mean stress is continuous. We report on the results of experiments designed to document failure criteria, fracture mode, and localization phenomena for several rock types (sandstone, limestone, chalk and marble). Experiments were conducted in triaxial extension using a necked (dogbone) geometry to achieve mixed tension and compression stress states with local component-strain measurements in the failure region. The failure envelope for all rock types is similar, but are poorly described using Griffith or modified Griffith (Coulomb or other) failure criteria. Notably, the mode of fracture changes systematically from pure extension to shear with increase in compressive mean stress and display a continuous change in fracture orientation with respect to principal stress axes. Differential stress and inelastic strain show a systematic increase with increasing mean stress, whereas the axial stress decreases before increasing with increasing mean stress. The stress and strain data are used to analyze elastic and plastic strains leading to failure and compare the experimental results to predictions for localization using constitutive models incorporating on bifurcation theory. Although models are able to describe the stability behavior and onset of localization qualitatively, the models are unable to predict fracture type or orientation. Constitutive models using single or multiple yield surfaces are unable to predict the experimental results, reflecting the difficulty in capturing the changing micromechanisms from extension to shear failure. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Deopartment of Energy's National Security Administration under contract DE-AC04-94AL85000. SAND2014-16578A

Metal Matrix Composites: Fatigue and Fracture Testing. (Latest citations from the Aerospace Database)

NASA Technical Reports Server (NTRS)

1996-01-01

The bibliography contains citations concerning techniques and results of testing metal matrix composites for fatigue and fracture. Methods include non-destructive testing techniques, and static and cyclic techniques for assessing compression, tensile, bending, and impact characteristics.

Biomechanical Property of a Newly Designed Assembly Locking Compression Plate: Three-Dimensional Finite Element Analysis

PubMed Central

Liu, Da

2017-01-01

In this study, we developed and validated a refined three-dimensional finite element model of middle femoral comminuted fracture to compare the biomechanical stability after two kinds of plate fixation: a newly designed assembly locking compression plate (NALCP) and a locking compression plate (LCP). CT data of a male volunteer was converted to middle femoral comminuted fracture finite element analysis model. The fracture was fixated by NALCP and LCP. Stress distributions were observed. Under slow walking load and torsion load, the stress distribution tendency of the two plates was roughly uniform. The anterolateral femur was the tension stress area, and the bone block shifted toward the anterolateral femur. Maximum stress was found on the lateral border of the number 5 countersink of the plate. Under a slow walking load, the NALCP maximum stress was 2.160e+03 MPa and the LCP was 8.561e+02 MPa. Under torsion load, the NALCP maximum stress was 2.260e+03 MPa and the LCP was 6.813e+02 MPa. Based on those results of finite element analysis, the NALCP can provide adequate mechanical stability for comminuted fractures, which would help fixate the bone block and promote bone healing. PMID:29065654

Evaluation of Varying Ductile Fracture Criteria for 42CrMo Steel by Compressions at Different Temperatures and Strain Rates

PubMed Central

Quan, Guo-zheng; Luo, Gui-chang; Mao, An; Liang, Jian-ting; Wu, Dong-sen

2014-01-01

Fracturing by ductile damage occurs quite naturally in metal forming processes, and ductile fracture of strain-softening alloy, here 42CrMo steel, cannot be evaluated through simple procedures such as tension testing. Under these circumstances, it is very significant and economical to find a way to evaluate the ductile fracture criteria (DFC) and identify the relationships between damage evolution and deformation conditions. Under the guidance of the Cockcroft-Latham fracture criteria, an innovative approach involving hot compression tests, numerical simulations, and mathematic computations provides mutual support to evaluate ductile damage cumulating process and DFC diagram along with deformation conditions, which has not been expounded by Cockcroft and Latham. The results show that the maximum damage value appears in the region of upsetting drum, while the minimal value appears in the middle region. Furthermore, DFC of 42CrMo steel at temperature range of 1123~1348 K and strain rate of 0.01~10 s−1 are not constant but change in a range of 0.160~0.226; thus, they have been defined as varying ductile fracture criteria (VDFC) and characterized by a function of temperature and strain rate. In bulk forming operations, VDFC help technicians to choose suitable process parameters and avoid the occurrence of fracture. PMID:24592175

Evaluation of varying ductile fracture criteria for 42CrMo steel by compressions at different temperatures and strain rates.

PubMed

Quan, Guo-zheng; Luo, Gui-chang; Mao, An; Liang, Jian-ting; Wu, Dong-sen

2014-01-01

Fracturing by ductile damage occurs quite naturally in metal forming processes, and ductile fracture of strain-softening alloy, here 42CrMo steel, cannot be evaluated through simple procedures such as tension testing. Under these circumstances, it is very significant and economical to find a way to evaluate the ductile fracture criteria (DFC) and identify the relationships between damage evolution and deformation conditions. Under the guidance of the Cockcroft-Latham fracture criteria, an innovative approach involving hot compression tests, numerical simulations, and mathematic computations provides mutual support to evaluate ductile damage cumulating process and DFC diagram along with deformation conditions, which has not been expounded by Cockcroft and Latham. The results show that the maximum damage value appears in the region of upsetting drum, while the minimal value appears in the middle region. Furthermore, DFC of 42CrMo steel at temperature range of 1123~1348 K and strain rate of 0.01~10 s(-1) are not constant but change in a range of 0.160~0.226; thus, they have been defined as varying ductile fracture criteria (VDFC) and characterized by a function of temperature and strain rate. In bulk forming operations, VDFC help technicians to choose suitable process parameters and avoid the occurrence of fracture.

Displaced intra-articular calcaneal fractures.

PubMed

Bajammal, Sohail; Tornetta, Paul; Sanders, David; Bhandari, Mohit

2005-01-01

Calcaneal fractures comprise 1 to 2 percent of all fractures. Approximately 75% of calcaneal fractures are intra-articular. The management of intra-articular calcaneal fractures remains controversial. Nonoperative treatment options include elevation, ice, early mobilization, and cyclic compression of the plantar arch. Operative treatment options include closed reduction and percutaneous pin fixation, open reduction and internal fixation, and arthrodesis. The effect of operative versus nonoperative treatment has been the focus of several comparative studies. This study was designed to determine the effect of operative treatment compared with nonoperative treatment on the rate of union, complications, and functional outcome after intra-articular calcaneal fracture in adults.

Locked compression plating for peri- and intra-articular fractures around the knee.

PubMed

Jain, Jitesh Kumar; Asif, Naiyer; Ahmad, Suhail; Qureshi, Owais; Siddiqui, Yasir Salam; Rana, Ashish

2013-11-01

To evaluate the role of locked compression plates (LCPs) in management of peri- and intra-articular fractures around the knee. Twenty distal femoral and 20 proximal tibial fractures were fixed with LCPs. The types of femoral fractures were A1 (four), A2 (three), A3 (two), C1 (one), C2 (seven) and C3 (three). The types of tibial fractures were A2 (one), A3 (two), B2 (two), C1 (four), C2 (five) and C3 (six). All patients were followed up for up to 18 months (mean, 12 months). Fourteen patients with distal femoral fractures and 19 with proximal tibial fractures underwent surgery using a minimally invasive percutaneous plate osteosynthesis (MIPPO) technique. The others were treated by open reduction. The average time of fixation was 8 days after injury (0-31 days). Knee Society scores were used for clinical and functional assessment. All fractures, except one of the distal femur and one of the proximal tibia, united. The mean union times for distal femoral and proximal tibial fractures were 15.2 and 14.9 weeks, respectively. One patient with a distal femoral fracture had implant failure. One patient was quadriplegic and did not recover the ability to walk. The average Knee Society scores of the remaining 18 patients were 82.66 (excellent) and 77.77 (functional score, good). There was one case of implant failure and one of screw breakage in distal femoral fractures. One case of nonunion occurred in a proximal tibial fracture. Provided it is applied with proper understanding of biomechanics, LCP is one of the best available options for management of challenging peri- and intra-articular fractures. © 2013 Chinese Orthopaedic Association and Wiley Publishing Asia Pty Ltd.

Do bisphosphonates inhibit direct fracture healing?: A laboratory investigation using an animal model.

PubMed

Savaridas, T; Wallace, R J; Salter, D M; Simpson, A H R W

2013-09-01

Fracture repair occurs by two broad mechanisms: direct healing, and indirect healing with callus formation. The effects of bisphosphonates on fracture repair have been assessed only in models of indirect fracture healing. A rodent model of rigid compression plate fixation of a standardised tibial osteotomy was used. Ten skeletally mature Sprague-Dawley rats received daily subcutaneous injections of 1 µg/kg ibandronate (IBAN) and ten control rats received saline (control). Three weeks later a tibial osteotomy was rigidly fixed with compression plating. Six weeks later the animals were killed. Fracture repair was assessed with mechanical testing, radiographs and histology. The mean stress at failure in a four-point bending test was significantly lower in the IBAN group compared with controls (8.69 Nmm(-2) (sd 7.63) vs 24.65 Nmm(-2) (sd 6.15); p = 0.017). On contact radiographs of the extricated tibiae the mean bone density assessment at the osteotomy site was lower in the IBAN group than in controls (3.7 mmAl (sd 0.75) vs 4.6 mmAl (sd 0.57); p = 0.01). In addition, histological analysis revealed progression to fracture union in the controls but impaired fracture healing in the IBAN group, with predominantly cartilage-like and undifferentiated mesenchymal tissue (p = 0.007). Bisphosphonate treatment in a therapeutic dose, as used for risk reduction in fragility fractures, had an inhibitory effect on direct fracture healing. We propose that bisphosphonate therapy not be commenced until after the fracture has united if the fracture has been rigidly fixed and is undergoing direct osteonal healing.

Anomaly in the dynamic strength of austenitic stainless steel 12Cr19Ni10Ti under shock wave loading

NASA Astrophysics Data System (ADS)

Garkushin, G. V.; Kanel, G. I.; Razorenov, S. V.; Savinykh, A. S.

2017-07-01

Measurement results for the shock wave compression profiles of 12Cr19Ni10Ti steel and its dynamic strength in the strain rate range 105-106 s-1 are presented. The protracted viscous character of the spall fracture is revealed. With the previously obtained data taken into account, the measurement results are described by a polynomial relation, which can be used to construct the fracture kinetics. On the lower boundary of the range, the resistance to spall fracture is close to the value of the true strength of the material under standard low-rate strain conditions; on the upper boundary, the spall strength is more than twice greater than this quantity. An increase in the temperature results in a decrease in both the dynamic limit of elasticity and the spall fracture strength of steel. The most interesting result is the anomaly in the dependence of the spall fracture strength on the duration of the shock wave compression pulse, which is related to the formation of deformation martensite near the growing discontinuities.

Fractographic study of the behavior of different ceramic veneers on full coverage crowns in relation to supporting core materials

PubMed Central

Agustín-Panadero, Rubén; Román-Rodriguez, Juan L.; Solá-Ruíz, María F.; Granell-Ruíz, María; Fons-Font, Antonio

2013-01-01

Objectives: To observe porcelain veneer behavior of zirconia and metal-ceramic full coverage crowns when subjected to compression testing, comparing zirconia cores to metal cores. Study Design: The porcelain fracture surfaces of 120 full coverage crowns (60 with a metal core and 60 with a zirconia core) subjected to static load (compression) testing were analyzed. Image analysis was performed using macroscopic processing with 8x and 12x enlargement. Five samples from each group were prepared and underwent scanning electron microscope (SEM) analysis in order to make a fractographic study of fracture propagation in the contact area and composition analysis in the most significant areas of the specimen. Results: Statistically significant differences in fracture type (cohesive or adhesive) were found between the metal-ceramic and zirconia groups: the incidence of adhesive fracture was seen to be greater in metal-ceramic groups (92%) and cohesive fracture was more frequent in zirconium oxide groups (72%). The fracture propagation pattern was on the periphery of the contact area in the full coverage crown restorations selected for fractographic study. Conclusions: The greater frequency of cohesive fracture in restorations with zirconia cores indicates that their behavior is inadequate compared to metal-ceramic restorations and that further research is needed to improve their clinical performance. Key words:Zirconia, zirconium oxide, fractography, composition, porcelain veneers, fracture, cohesive, adhesive. PMID:24455092

Insights into the effects of tensile and compressive loadings on human femur bone.

PubMed

Havaldar, Raviraj; Pilli, S C; Putti, B B

2014-01-01

Fragile fractures are most likely manifestations of fatigue damage that develop under repetitive loading conditions. Numerous microcracks disperse throughout the bone with the tensile and compressive loads. In this study, tensile and compressive load tests are performed on specimens of both the genders within 19 to 83 years of age and the failure strength is estimated. Fifty five human femur cortical samples are tested. They are divided into various age groups ranging from 19-83 years. Mechanical tests are performed on an Instron 3366 universal testing machine, according to American Society for Testing and Materials International (ASTM) standards. The results show that stress induced in the bone tissue depends on age and gender. It is observed that both tensile and compression strengths reduces as age advances. Compressive strength is more than tensile strength in both the genders. The compression and tensile strength of human femur cortical bone is estimated for both male and female subjecting in the age group of 19-83 years. The fracture toughness increases till 35 years in male and 30 years in female and reduces there after. Mechanical properties of bone are age and gender dependent.

Direct Shear Tests of Sandstone Under Constant Normal Tensile Stress Condition Using a Simple Auxiliary Device

NASA Astrophysics Data System (ADS)

Cen, Duofeng; Huang, Da

2017-06-01

Tension-shear failure is a typical failure mode in the rock masses in unloading zones induced by excavation or river incision, etc., such as in excavation-disturbed zone of deep underground caverns and superficial rocks of high steep slopes. However, almost all the current shear failure criteria for rock are usually derived on the basis of compression-shear failure. This paper proposes a simple device for use with a servo-controlled compression-shear testing machine to conduct the tension-shear tests of cuboid rock specimens, to test the direct shear behavior of sandstone under different constant normal tensile stress conditions ( σ = -1, -1.5, -2, -2.5 and -3 MPa) as well as the uniaxial tension behavior. Generally, the fracture surface roughness decreases and the proportion of comminution areas in fracture surface increases as the change of stress state from tension to tension-shear and to compression-shear. Stepped fracture is a primary fracture pattern in the tension-shear tests. The shear stiffness, shear deformation and normal deformation (except the normal deformation for σ = -1 MPa) decrease during shearing, while the total normal deformation containing the pre-shearing portion increases as the normal tensile stress level (| σ|) goes up. Shear strength is more sensitive to the normal tensile stress than to the normal compressive stress, and the power function failure criterion (or Mohr envelope form of Hoek-Brown criterion) is examined to be the optimal criterion for the tested sandstone in the full region of tested normal stress in this study.

Biomechanical analysis of fixation of middle third fractures of the clavicle.

PubMed

Drosdowech, Darren S; Manwell, Stuart E E; Ferreira, Louis M; Goel, Danny P; Faber, Kenneth J; Johnson, James A

2011-01-01

This biomechanical study compares four different techniques of fixation of middle third clavicular fractures. Twenty fresh-frozen clavicles were randomized into four groups. Each group used a different fixation device (3.5 Synthes reconstruction plate, 3.5 Synthes limited contact dynamic compression plate, 3.5 Synthes locking compression plate, and 4.5 DePuy Rockwood clavicular pin). All constructs were mechanically tested in bending and torque modes both with and without a simulated inferior cortical defect. Bending load to failure was also conducted. The four groups were compared using an analysis of variance test. The plate constructs were stiffer than the pin during both pure bending and torque loads with or without an inferior cortical defect. Bending load to failure with an inferior cortical defect revealed that the reconstruction plate was weaker compared with the other three groups. The limited contact and locking plates were stiffer than the reconstruction plate but demonstrated statistical significance only with the cortical defect. As hypothesized, the 3.5 limited contact dynamic compression plate and 3.5 locking compression plate demonstrated the greatest resistance to bending and torque loads, especially in the presence of simulated comminution of a middle third clavicular fracture. The reconstruction plate demonstrated lower stiffness and strength values compared with the other plates, especially with a cortical defect, whereas the pin showed poor resistance to bending and torque loads in all modes of testing. This information may help surgeons to choose the most appropriate method of fixation when treating fractures of the middle third of the clavicle.

An Experimental and Numerical Study on Cracking Behavior of Brittle Sandstone Containing Two Non-coplanar Fissures Under Uniaxial Compression

NASA Astrophysics Data System (ADS)

Yang, Sheng-Qi; Tian, Wen-Ling; Huang, Yan-Hua; Ranjith, P. G.; Ju, Yang

2016-04-01

To understand the fracture mechanism in all kinds of rock engineering, it is important to investigate the fracture evolution behavior of pre-fissured rock. In this research, we conducted uniaxial compression experiments to evaluate the influence of ligament angle on the strength, deformability, and fracture coalescence behavior of rectangular prismatic specimens (80 × 160 × 30 mm) of brittle sandstone containing two non-coplanar fissures. The experimental results show that the peak strength of sandstone containing two non-coplanar fissures depends on the ligament angle, but the elastic modulus is not closely related to the ligament angle. With the increase of ligament angle, the peak strength decreased at a ligament angle of 60°, before increasing up to our maximum ligament angle of 120°. Crack initiation, propagation, and coalescence were all observed and characterized from the inner and outer tips of pre-existing non-coplanar fissures using photographic monitoring. Based on the results, the sequence of crack evolution in sandstone containing two non-coplanar fissures was analyzed in detail. In order to fully understand the crack evolution mechanism of brittle sandstone, numerical simulations using PFC2D were performed for specimens containing two non-coplanar fissures under uniaxial compression. The results are in good agreement with the experimental results. By analyzing the stress field, the crack evolution mechanism in brittle sandstone containing two non-coplanar fissures under uniaxial compression is revealed. These experimental and numerical results are expected to improve the understanding of the unstable fracture mechanism of fissured rock engineering structures.

Sacral Stress Fracture Mimicking Lumbar Radiculopathy in a Mounted Police Officer: Case Report and Literature Review.

PubMed

Bednar, Drew A; Almansoori, Khaled

2015-10-01

Study Design Case report and review of the literature. Objective To present a unique case of L5 radiculopathy caused by a sacral stress fracture without neurologic compression. Methods We present our case and its clinical evolution and review the available literature on similar pathologies. Results Relief of the unusual mechanical loading causing sacral stress fracture led to rapid resolution of radiculopathy. Conclusion L5 radiculopathy can be caused by a sacral stress fracture and can be relieved by simple mechanical treatment of the fracture.

Compression and contact area of anterior strut grafts in spinal instrumentation: a biomechanical study.

PubMed

Pizanis, Antonius; Holstein, Jörg H; Vossen, Felix; Burkhardt, Markus; Pohlemann, Tim

2013-08-26

Anterior bone grafts are used as struts to reconstruct the anterior column of the spine in kyphosis or following injury. An incomplete fusion can lead to later correction losses and compromise further healing. Despite the different stabilizing techniques that have evolved, from posterior or anterior fixating implants to combined anterior/posterior instrumentation, graft pseudarthrosis rates remain an important concern. Furthermore, the need for additional anterior implant fixation is still controversial. In this bench-top study, we focused on the graft-bone interface under various conditions, using two simulated spinal injury models and common surgical fixation techniques to investigate the effect of implant-mediated compression and contact on the anterior graft. Calf spines were stabilised with posterior internal fixators. The wooden blocks as substitutes for strut grafts were impacted using a "pressfit" technique and pressure-sensitive films placed at the interface between the vertebral bone and the graft to record the compression force and the contact area with various stabilization techniques. Compression was achieved either with posterior internal fixator alone or with an additional anterior implant. The importance of concomitant ligament damage was also considered using two simulated injury models: pure compression Magerl/AO fracture type A or rotation/translation fracture type C models. In type A injury models, 1 mm-oversized grafts for impaction grafting provided good compression and fair contact areas that were both markedly increased by the use of additional compressing anterior rods or by shortening the posterior fixator construct. Anterior instrumentation by itself had similar effects. For type C injuries, dramatic differences were observed between the techniques, as there was a net decrease in compression and an inadequate contact on the graft occurred in this model. Under these circumstances, both compression and the contact area on graft could only be maintained at high levels with the use of additional anterior rods. Under experimental conditions, we observed that ligamentous injury following type C fracture has a negative influence on the compression and contact area of anterior interbody bone grafts when only an internal fixator is used for stabilization. Because of the loss of tension banding effects in type C injuries, an additional anterior compressing implant can be beneficial to restore both compression to and contact on the strut graft.

The chopstick-noodle twist: an easy technique of percutaneous patellar fixation in minimally displaced patellar fractures.

PubMed

Muzaffar, Nasir; Ahmad, Nawaz; Ahmad, Aejaz; Ahmad, Nissar

2012-01-01

We report six cases of minimally displaced two-part patellar fractures with skin injury over the patella that were treated with percutaneous K wire fixation and compression applied using stainless steel (SS) wire. This technique makes it possible to perform early operative treatment in cases where unhealthy skin is not amenable to conventional tension band wiring. The technique employs two K wires inserted through the two fracture fragments under local or regional anaesthesia. They are then compressed using simple SS wire knots at the two ends - making it look like noodles at the end of two chopsticks. The fixation is subsequently augmented with a cylindrical plaster-of-Paris cast. The technique is simple, cheap and does not cause soft tissue injury.

A biomechanical evaluation of a cannulated compressive screw for use in fractures of the scaphoid.

PubMed

Rankin, G; Kuschner, S H; Orlando, C; McKellop, H; Brien, W W; Sherman, R

1991-11-01

The compressive force generated by a 3.5 mm ASIF cannulated cancellous screw with a 5 mm head was compared with that generated by a standard 3.5 mm ASIF screw (6 mm head), a 2.7 mm ASIF screw (5 mm head), and a Herbert screw. The screws were evaluated in the laboratory with the use of a custom-designed load washer (transducer) to the maximum compressive force generated by each screw until failure, either by thread stripping or by head migration into the specimen. Testing was done on paired cadaver scaphoids. To minimize the variability that occurs with human bone, and because of the cost and difficulty of obtaining human tissue specimens, a study was also done on polyurethane foam simulated bones. The 3.5 cannulated screw generated greater compressive forces than the Herbert screw but less compression than the 2.7 mm and 3.5 mm ASIF cortical screws. The 3.5 mm cannulated screw offers more rigid internal fixation for scaphoid fractures than the Herbert screw and gives the added advantage of placement over a guide wire.

3D Experimental Measurement of Lattice Strain and Fracture Behavior of Sand Particles Using Synchrotron X-Ray Diffraction and Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cil, Mehmet B.; Alshibli, Khalid A.; Kenesei, Peter

3D synchrotron X-ray diffraction (3DXRD) and synchrotron micro-computed tomography (SMT) techniques were used to measure and monitor the lattice strain evolution and fracture behavior of natural Ottawa sand particles subjected to 1D compression loading. The particle-averaged lattice strain within sand particles was measured using 3DXRD and then was used to calculate the corresponding lattice stress tensor. In addition, the evolution and mode of fracture of sand particles was investigated using high-resolution 3D SMT images. The results of diffraction data analyses revealed that the major principal component of the lattice strain or stress tensor increased in most of the particles asmore » the global applied compressive load increased until the onset of fracture. Particle fracture and subsequent rearrangements caused significant variation and fluctuations in measured lattice strain/stress values from one particle to another and from one load step to the next one. SMT image analysis at the particle-scale showed that cracks in fractured sand particles generally initiate and propagate along the plane that connects the two contact points. Fractured particles initially split into two or three major fragments followed by disintegration into multiple smaller fragments in some cases. In conclusion, microscale analysis of fractured particles showed that particle position, morphology, the number and location of contact points play a major role in the occurrence of particle fracture in confined comminution of the sand assembly.« less

3D Experimental Measurement of Lattice Strain and Fracture Behavior of Sand Particles Using Synchrotron X-Ray Diffraction and Tomography

DOE PAGES

Cil, Mehmet B.; Alshibli, Khalid A.; Kenesei, Peter

2017-05-27

3D synchrotron X-ray diffraction (3DXRD) and synchrotron micro-computed tomography (SMT) techniques were used to measure and monitor the lattice strain evolution and fracture behavior of natural Ottawa sand particles subjected to 1D compression loading. The particle-averaged lattice strain within sand particles was measured using 3DXRD and then was used to calculate the corresponding lattice stress tensor. In addition, the evolution and mode of fracture of sand particles was investigated using high-resolution 3D SMT images. The results of diffraction data analyses revealed that the major principal component of the lattice strain or stress tensor increased in most of the particles asmore » the global applied compressive load increased until the onset of fracture. Particle fracture and subsequent rearrangements caused significant variation and fluctuations in measured lattice strain/stress values from one particle to another and from one load step to the next one. SMT image analysis at the particle-scale showed that cracks in fractured sand particles generally initiate and propagate along the plane that connects the two contact points. Fractured particles initially split into two or three major fragments followed by disintegration into multiple smaller fragments in some cases. In conclusion, microscale analysis of fractured particles showed that particle position, morphology, the number and location of contact points play a major role in the occurrence of particle fracture in confined comminution of the sand assembly.« less

Dynamic compressive behavior of Pr-Nd alloy at high strain rates and temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Huanran; Cai Canyuan; Chen Danian

2012-07-01

Based on compressive tests, static on 810 material test system and dynamic on the first compressive loading in split Hopkinson pressure bar (SHPB) tests for Pr-Nd alloy cylinder specimens at high strain rates and temperatures, this study determined a J-C type [G. R. Johnson and W. H. Cook, in Proceedings of Seventh International Symposium on Ballistics (The Hague, The Netherlands, 1983), pp. 541-547] compressive constitutive equation of Pr-Nd alloy. It was recorded by a high speed camera that the Pr-Nd alloy cylinder specimens fractured during the first compressive loading in SHPB tests at high strain rates and temperatures. From highmore » speed camera images, the critical strains of the dynamic shearing instability for Pr-Nd alloy in SHPB tests were determined, which were consistent with that estimated by using Batra and Wei's dynamic shearing instability criterion [R. C. Batra and Z. G. Wei, Int. J. Impact Eng. 34, 448 (2007)] and the determined compressive constitutive equation of Pr-Nd alloy. The transmitted and reflected pulses of SHPB tests for Pr-Nd alloy cylinder specimens computed with the determined compressive constitutive equation of Pr-Nd alloy and Batra and Wei's dynamic shearing instability criterion could be consistent with the experimental data. The fractured Pr-Nd alloy cylinder specimens of compressive tests were investigated by using 3D supper depth digital microscope and scanning electron microscope.« less

Fracture resistance of five pin-retained core build-up materials on teeth with and without extracoronal preparation.

PubMed

Burke, F J; Shaglouf, A G; Combe, E C; Wilson, N H

2000-01-01

Core build-ups should provide satisfactory strength and resistance to fracture both before and after crown preparation. This paper examines the resistance to fracture of core build-ups in different materials and the fracture resistance of core build-ups when these have been reduced for full crown preparation. Standardized core build-ups were made on groups of extracted molar teeth of similar size, with 10 teeth per group. Three resin-composite (prisma APH: Dentsply, Weybridge, UK; Ti-Core, Essential Dental Systems, NJ, US and Coradent, Vivadent, Liechtenstein), one cermet (Ketac-Silver, ESPE GmbH, Seefeld, Germany) and one amalgam material (Duralloy, Degussa Ltd, Cheshire, UK). These specimens were subjected to compressive force on a universal testing machine and the force at fracture noted. Standardized full crown preparations were made on a further five groups of core build-up specimens using the same materials as above. These prepared specimens were subjected to compressive force on a universal testing machine and the force to fracture noted. The results indicated that amalgam core build-ups demonstrated higher fracture resistance than the other materials examined. There was a general decrease in the fracture strength of the specimens following crown preparation, with the teeth restored with the amalgam core build-ups showing a greater percentage reduction in fracture strength than the other materials tested. Prepared core build-ups in a hybrid composite material provided the highest fracture resistance. The cermet material used provided the lowest resistance to fracture in both the core build-up and crown preparation specimens. In terms of fracture resistance, no advantage was apparent in using the two composite materials designated as being specifically appropriate for core build-ups.

Experimental investigation of the strength and failure behavior of layered sandstone under uniaxial compression and Brazilian testing

NASA Astrophysics Data System (ADS)

Yin, Peng-Fei; Yang, Sheng-Qi

2018-05-01

As a typical inherently anisotropic rock, layered sandstones can differ from each other in several aspects, including grain size, type of material, type of cementation, and degree of compaction. An experimental study is essential to obtain and convictive evidence to characterize the mechanical behavior of such rock. In this paper, the mechanical behavior of a layered sandstone from Xuzhou, China, is investigated under uniaxial compression and Brazilian test conditions. The loading tests are conducted on 7 sets of bedding inclinations, which are defined as the angle between the bedding plane and horizontal direction. The uniaxial compression strength (UCS) and elastic modulus values show an undulatory variation when the bedding inclination increases. The overall trend of the UCS and elastic modulus values with bedding inclination is decreasing. The BTS value decreases with respect to the bedding inclination and the overall trend of it is approximating a linear variation. The 3D digital high-speed camera images reveal that the failure and fracture of a specimen are related to the surface deformation. Layered sandstone tested under uniaxial compression does not show a typical failure mode, although shear slip along the bedding plane occurs at high bedding inclinations. Strain gauge readings during the Brazilian tests indicate that the normal stress on the bedding plane transforms from compression to tension as the bedding inclination increases. The stress parallel to the bedding plane in a rock material transforms from tension to compression and agrees well with the fracture patterns; "central fractures" occur at bedding inclinations of 0°-75°, "layer activation" occurs at high bedding inclinations of 75°-90°, and a combination of the two occurs at 75°.

Compression Fracture of CFRP Laminates Containing Stress Intensifications.

PubMed

Leopold, Christian; Schütt, Martin; Liebig, Wilfried V; Philipkowski, Timo; Kürten, Jonas; Schulte, Karl; Fiedler, Bodo

2017-09-05

For brittle fracture behaviour of carbon fibre reinforced plastics (CFRP) under compression, several approaches exist, which describe different mechanisms during failure, especially at stress intensifications. The failure process is not only initiated by the buckling fibres, but a shear driven fibre compressive failure beneficiaries or initiates the formation of fibres into a kink-band. Starting from this kink-band further damage can be detected, which leads to the final failure. The subject of this work is an experimental investigation on the influence of ply thickness and stacking sequence in quasi-isotropic CFRP laminates containing stress intensifications under compression loading. Different effects that influence the compression failure and the role the stacking sequence has on damage development and the resulting compressive strength are identified and discussed. The influence of stress intensifications is investigated in detail at a hole in open hole compression (OHC) tests. A proposed interrupted test approach allows identifying the mechanisms of damage initiation and propagation from the free edge of the hole by causing a distinct damage state and examine it at a precise instant of time during fracture process. Compression after impact (CAI) tests are executed in order to compare the OHC results to a different type of stress intensifications. Unnotched compression tests are carried out for comparison as a reference. With this approach, a more detailed description of the failure mechanisms during the sudden compression failure of CFRP is achieved. By microscopic examination of single plies from various specimens, the different effects that influence the compression failure are identified. First damage of fibres occurs always in 0°-ply. Fibre shear failure leads to local microbuckling and the formation and growth of a kink-band as final failure mechanisms. The formation of a kink-band and finally steady state kinking is shifted to higher compressive strains with decreasing ply thickness. Final failure mode in laminates with stress intensification depends on ply thickness. In thick or inner plies, damage initiates as shear failure and fibre buckling into the drilled hole. The kink-band orientation angle is changing with increasing strain. In outer or thin plies shear failure of single fibres is observed as first damage and the kink-band orientation angle is constant until final failure. Decreasing ply thickness increases the unnotched compressive strength. When stress intensifications are present, the position of the 0°-layer is critical for stability under compression and is thus more important than the ply thickness. Central 0°-layers show best results for OHC and CAI strength due to higher bending stiffness and better supporting effect of the adjacent layers.

Compression Fracture of CFRP Laminates Containing Stress Intensifications

PubMed Central

Schütt, Martin; Philipkowski, Timo; Kürten, Jonas; Schulte, Karl

2017-01-01

For brittle fracture behaviour of carbon fibre reinforced plastics (CFRP) under compression, several approaches exist, which describe different mechanisms during failure, especially at stress intensifications. The failure process is not only initiated by the buckling fibres, but a shear driven fibre compressive failure beneficiaries or initiates the formation of fibres into a kink-band. Starting from this kink-band further damage can be detected, which leads to the final failure. The subject of this work is an experimental investigation on the influence of ply thickness and stacking sequence in quasi-isotropic CFRP laminates containing stress intensifications under compression loading. Different effects that influence the compression failure and the role the stacking sequence has on damage development and the resulting compressive strength are identified and discussed. The influence of stress intensifications is investigated in detail at a hole in open hole compression (OHC) tests. A proposed interrupted test approach allows identifying the mechanisms of damage initiation and propagation from the free edge of the hole by causing a distinct damage state and examine it at a precise instant of time during fracture process. Compression after impact (CAI) tests are executed in order to compare the OHC results to a different type of stress intensifications. Unnotched compression tests are carried out for comparison as a reference. With this approach, a more detailed description of the failure mechanisms during the sudden compression failure of CFRP is achieved. By microscopic examination of single plies from various specimens, the different effects that influence the compression failure are identified. First damage of fibres occurs always in 0°-ply. Fibre shear failure leads to local microbuckling and the formation and growth of a kink-band as final failure mechanisms. The formation of a kink-band and finally steady state kinking is shifted to higher compressive strains with decreasing ply thickness. Final failure mode in laminates with stress intensification depends on ply thickness. In thick or inner plies, damage initiates as shear failure and fibre buckling into the drilled hole. The kink-band orientation angle is changing with increasing strain. In outer or thin plies shear failure of single fibres is observed as first damage and the kink-band orientation angle is constant until final failure. Decreasing ply thickness increases the unnotched compressive strength. When stress intensifications are present, the position of the 0°-layer is critical for stability under compression and is thus more important than the ply thickness. Central 0°-layers show best results for OHC and CAI strength due to higher bending stiffness and better supporting effect of the adjacent layers. PMID:28872623

Femur loading in feet-first fall experiments using an anthropomorphic test device.

PubMed

Thompson, Angela; Bertocci, Gina; Smalley, Craig

2018-03-31

Femur fractures are a common orthopedic injury in young children. Falls account for a large portion of accidental femur fractures in young children, but there is also a high prevalence of femur fractures in child abuse, with falls often provided as false histories. Objective information regarding fracture potential in short distance fall scenarios may aid in assessing whether a child's injuries are the result of abuse or an accidental fall. Knowledge of femur loading is the first step towards understanding likelihood of fracture in a fall. Characterize femur loading during feet-first free falls using a surrogate representing a 12-month-old child. The femur and hip joint of a surrogate representing a 12-month-old were modified to improve biofidelity and measure femur loading; 6-axis load cells were integrated into the proximal and distal femur. Femur modification was based upon CT imaging of cadaveric femurs in children 10-14 months of age. Using the modified 12-month-old surrogate, feet-first free falls from 69 cm and 119 cm heights onto padded carpet and linoleum were conducted to assess fall dynamics and determine femur loading. Femur compression, bending moment, shear and torsional moment were measured for each fall. Fall dynamics differed across fall heights, but did not substantially differ by impact surface type. Significant differences were found in all loading conditions across fall heights, while only compression and bending loads differed between carpet and linoleum surfaces. Maximum compression, bending, torsion and shear occurred in 119 cm falls and were 572 N, 23 N-m, 11 N-m and 281 N, respectively. Fall dynamics play an important role in the biomechanical assessment of falls. Fall height was found to influence both fall dynamics and femur loading, while impact surface affected only compression and bending in feet-first falls; fall dynamics did not differ across carpet and linoleum. Improved pediatric thresholds are necessary to predict likelihood of fracture, but morphologically accurate representation of the lower extremity, along with accurate characterization of loading in falls are a crucial first step. Copyright © 2018 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

Transverse stresses and modes of failure in tree branches and other beams.

PubMed

Ennos, A R; van Casteren, A

2010-04-22

The longitudinal stresses in beams subjected to bending also set up transverse stresses within them; they compress the cross section when the beam's curvature is being increased and stretch it when its curvature is being reduced. Analysis shows that transverse stresses rise to a maximum at the neutral axis and increase with both the bending moment applied and the curvature of the beam. These stresses can qualitatively explain the fracture behaviour of tree branches. Curved 'hazard beams' that are being straightened split down the middle because of the low transverse tensile strength of wood. By contrast, straight branches of light wood buckle when they are bent because of its low transverse compressive strength. Branches of denser wood break, but the low transverse tensile strength diverts the crack longitudinally when the fracture has only run half-way across the beam, to produce their characteristic 'greenstick fracture'. The bones of young mammals and uniaxially reinforced composite beams may also be prone to greenstick fracture because of their lower transverse tensile strength.

[Vertebroplasty: state of the art].

PubMed

Chiras, J; Barragán-Campos, H M; Cormier, E; Jean, B; Rose, M; LeJean, L

2007-09-01

Over the last 10 years, there has been much development in the management of metastatic and osteoporotic vertebral compression fractures using vertebroplasty. This percutaneous image-guided interventional radiology procedure allows stabilization of a vertebral body by injection of an acrylic cement and frequently results in significant symptomatic relief. During cement polymerisation, an exothermic reaction may destroy adjacent tumor cells. Advances have been made to reduce complications from extravasation of cement in veins or surrounding soft tissues. Safety relates to experience but also to technical parameters: optimal cement radio-density, adequate digital fluoroscopy unit (single or bi-plane digital angiography unit), development of cements other than PMMA to avoid the risk of adjacent vertebral compression fractures. The rate of symptomatic relief from vertebroplasty performed for its principal indications (vertebral hemangioma, metastases, osteoporotic fractures) reaches 90-95%. The rate of complications is about 2% for metastases and less than 0.5% for osteoporotic fractures. Vertebroplasty plays a major role in the management of specific bone weakening vertebral lesions causing, obviating the need for kyphoplasty.

Biomechanical analysis of tension band fixation for olecranon fracture treatment.

PubMed

Kozin, S H; Berglund, L J; Cooney, W P; Morrey, B F; An, K N

1996-01-01

This study assessed the strength of various tension band fixation methods with wire and cable applied to simulated olecranon fractures to compare stability and potential failure or complications between the two. Transverse olecranon fractures were simulated by osteotomy. The fracture was anatomically reduced, and various tension band fixation techniques were applied with monofilament wire or multifilament cable. With a material testing machine load displacement curves were obtained and statistical relevance determined by analysis of variance. Two loading modes were tested: loading on the posterior surface of olecranon to simulate triceps pull and loading on the anterior olecranon tip to recreate a potential compressive loading on the fragment during the resistive flexion. All fixation methods were more resistant to posterior loading than to an anterior load. Individual comparative analysis for various loading conditions concluded that tension band fixation is more resilient to tensile forces exerted by the triceps than compressive forces on the anterior olecranon tip. Neither wire passage anterior to the K-wires nor the multifilament cable provided statistically significant increased stability.

Factors affecting the thermal shock behavior of yttria stabilized hafnia based graphite and tungsten composites.

NASA Technical Reports Server (NTRS)

Lineback, L. D.; Manning, C. R.

1971-01-01

Hafnia-based composites containing either graphite or tungsten were investigated as rocket nozzle throat inserts in solid propellant rocket engines. The thermal shock resistance of these materials is considered in terms of macroscopic thermal conductivity, thermal expansion, modulus of elasticity, and compressive fracture stress. The effect of degree of hafnia stabilization, density, and graphite or tungsten content upon these parameters is discussed. The variation of the ratio of elastic modulus to compressive fracture stress with density and its effect upon thermal shock resistance of these materials are discussed in detail.

Dynamic hip system blade versus cannulated compression screw for the treatment of femoral neck fractures: A retrospective study.

PubMed

Chen, Chao; Yu, Li; Tang, Xin; Liu, Mo-Zhen; Sun, Li-Zhong; Liu, Changjian; Zhang, Zhen; Li, Chang-Zhou

2017-10-01

The aim of this study was to compare clinical outcomes of patients with femoral neck fractures treated with the dynamic hip system blade (DHS-BLADE) or cannulated compression screws. Eighty-six patients with femoral neck fractures were treated by closed reduction internal fixation with a DHS-BLADE (n = 42; 18 males and 24 females; mean age: 56.3 years (37-87)) or cannulated compression screws (n = 44; 20 males and 24 females; mean age: 53.8 years (26-83)) between March 2011 and August 2013. The groups were compared with Harris hip score, operation time, surgical blood loss, incision size, hospital stay, and related complications. The average follow-up time was 27 months (range, 24-36 months). There was no significant difference for the operation time, incision size, hospital stay, and Harris hip score between the groups. Also, no statistically significant differences in the rates of nonunion (4.5% vs. 0) and avascular necrosis of the femoral head (9.1% vs. 7.1%) were observed. However, the screw group experienced significantly less surgical blood loss (32.4 ± 24.7 ml) than the blade group (87.2 ± 46.6 ml; P = 0.041). The incidence of femoral neck shortening above 10 mm in the screw group was significantly higher than that in the blade group (15.9% vs. 2.4%, P = 0.031). The blade group had a significantly lower incidence of screw migration than the screw group (4.8% vs. 22.7%, P = 0.016). The DHS-BLADE and cannulated compression screws might be equally effective in terms of postoperative fracture union. However, the DHS-BLADE has advantages over cannulated compression screws for preventing femoral neck shortening, screw migration, and cut-out. Level III, Therapeutic study. Copyright © 2017 Turkish Association of Orthopaedics and Traumatology. Production and hosting by Elsevier B.V. All rights reserved.

Damage Tolerance of Sandwich Plates with Debonded Face Sheets

NASA Technical Reports Server (NTRS)

Avery, John L., III; Sankar, Bhavani V.

1998-01-01

Axial compression tests were performed on debonded sandwich composites made of graphite/epoxy face-sheets and aramid fiber honeycomb core. The sandwich beams were manufactured using a vacuum baccrin2 process. The face-sheet and the sandwich beam were co-cured. Delamination between one of the face sheets and the core was introduced by using a Teflon layer during the curing process. Axial compression tests were performed to determine the ultimate load carrying capacity of the debonded beams. Flatwise tension tests and Double Cantilever Beam tests were performed to determine. respectively, the strength and fracture toughness of the face-sheet/core interface. From the test results semi-empirical formulas were derived for the fracture toughness and ultimate compressive load carrying capacity in terms of the core density. core thickness. face-sheet thickness and debond length. Four different failure modes and their relation to the structural properties were identified. Linear buckling analysis was found to be inadequate in predicting the compressive load carrying capacity of the debonded sandwich composites.

Experimental and computational correlation of fracture parameters KIc, JIc, and GIc for unimodular and bimodular graphite components

NASA Astrophysics Data System (ADS)

Bhushan, Awani; Panda, S. K.

2018-05-01

The influence of bimodularity (different stress ∼ strain behaviour in tension and compression) on fracture behaviour of graphite specimens has been studied with fracture toughness (KIc), critical J-integral (JIc) and critical strain energy release rate (GIc) as the characterizing parameter. Bimodularity index (ratio of tensile Young's modulus to compression Young's modulus) of graphite specimens has been obtained from the normalized test data of tensile and compression experimentation. Single edge notch bend (SENB) testing of pre-cracked specimens from the same lot have been carried out as per ASTM standard D7779-11 to determine the peak load and critical fracture parameters KIc, GIc and JIc using digital image correlation technology of crack opening displacements. Weibull weakest link theory has been used to evaluate the mean peak load, Weibull modulus and goodness of fit employing two parameter least square method (LIN2), biased (MLE2-B) and unbiased (MLE2-U) maximum likelihood estimator. The stress dependent elasticity problem of three-dimensional crack progression behaviour for the bimodular graphite components has been solved as an iterative finite element procedure. The crack characterizing parameters critical stress intensity factor and critical strain energy release rate have been estimated with the help of Weibull distribution plot between peak loads versus cumulative probability of failure. Experimental and Computational fracture parameters have been compared qualitatively to describe the significance of bimodularity. The bimodular influence on fracture behaviour of SENB graphite has been reflected on the experimental evaluation of GIc values only, which has been found to be different from the calculated JIc values. Numerical evaluation of bimodular 3D J-integral value is found to be close to the GIc value whereas the unimodular 3D J-value is nearer to the JIc value. The significant difference between the unimodular JIc and bimodular GIc indicates that GIc should be considered as the standard fracture parameter for bimodular brittle specimens.

Effect of cryogenic treatment on the fracture toughness of aircraft aluminum alloy 7075

NASA Astrophysics Data System (ADS)

Ermishkin, V. A.; Soloveva, Y. B.

2018-04-01

Influence of three types of the treatment on fracture toughness of the Al-7075 alloy was investigated in this study. Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by hardening with post-cryogenic deformation treatment and PVD deposition titanium and copper coatings. The fracture toughness was estimated with using macroscopic and microscopic approaches. The conditions for the coincidence of the fracture toughness estimates between brittle fracture mechanics and the photometric analysis of structural images (PHASI) methods were achieved. The highest fracture toughness was obtained by applying hardening, cryogenic compression, ageing and deposition of the Ti-coating, leading to dispersion particles precipitation.

Effect of fluid penetration on tensile failure during fracturing of an open-hole wellbore

NASA Astrophysics Data System (ADS)

Zeng, Fanhui; Cheng, Xiaozhao; Guo, Jianchun; Chen, Zhangxin; Tao, Liang; Liu, Xiaohua; Jiang, Qifeng; Xiang, Jianhua

2018-06-01

It is widely accepted that a fracture can be induced at a wellbore surface when the fluid pressure overcomes the rock tensile strength. However, few models of this phenomenon account for the fluid penetration effect. A rock is a typical permeable, porous medium, and the transmission of pressure from a wellbore to the surrounding rock temporally and spatially perturbs the effective stresses. In addition, these induced stresses influence the fracture initiation pressure. To gain a better understanding of the penetration effect on the initiation pressure of a permeable formation, a comprehensive formula is presented to study the effects of the in situ stresses, rock mechanical properties, injection rate, rock permeability, fluid viscosity, fluid compressibility and wellbore size on the magnitude of the initiation pressure during fracturing of an open-hole wellbore. In this context, the penetration effect is treated as a consequence of the interaction among these parameters by using Darcy’s law of radial flow. A fully coupled analytical procedure is developed to show how the fracturing fluid infiltrates the rock around the wellbore and considerably reduces the magnitude of the initiation pressure. Moreover, the calculation results are validated by hydraulic fracturing experiments in hydrostone. An exhaustive sensitivity study is performed, indicating that the local fluid pressure induced from a seepage effect strongly influences the fracture evolution. For permeable reservoirs, a low injection rate and a low viscosity of the injected fluid have a significant impact on the fracture initiation pressure. In this case, the Hubbert and Haimson equations to predict the fracture initiation pressure are not valid. The open-hole fracture initiation pressure increases with the fracturing fluid viscosity and fluid compressibility, while it decreases as the rock permeability, injection rate and wellbore size increase.

Fracture behavior of human molars.

PubMed

Keown, Amanda J; Lee, James J-W; Bush, Mark B

2012-12-01

Despite the durability of human teeth, which are able to withstand repeated loading while maintaining form and function, they are still susceptible to fracture. We focus here on longitudinal fracture in molar teeth-channel-like cracks that run along the enamel sidewall of the tooth between the gum line (cemento-enamel junction-CEJ) and the occlusal surface. Such fractures can often be painful and necessitate costly restorative work. The following study describes fracture experiments made on molar teeth of humans in which the molars are placed under axial compressive load using a hard indenting plate in order to induce longitudinal cracks in the enamel. Observed damage modes include fractures originating in the occlusal region ('radial-median cracks') and fractures emanating from the margin of the enamel in the region of the CEJ ('margin cracks'), as well as 'spalling' of enamel (the linking of longitudinal cracks). The loading conditions that govern fracture behavior in enamel are reported and observations made of the evolution of fracture as the load is increased. Relatively low loads were required to induce observable crack initiation-approximately 100 N for radial-median cracks and 200 N for margin cracks-both of which are less than the reported maximum biting force on a single molar tooth of several hundred Newtons. Unstable crack growth was observed to take place soon after and occurred at loads lower than those calculated by the current fracture models. Multiple cracks were observed on a single cusp, their interactions influencing crack growth behavior. The majority of the teeth tested in this study were noted to exhibit margin cracks prior to compression testing, which were apparently formed during the functional lifetime of the tooth. Such teeth were still able to withstand additional loading prior to catastrophic fracture, highlighting the remarkable damage containment capabilities of the natural tooth structure.

Thoracolumbar spine fractures in frontal impact crashes.

PubMed

Pintar, Frank A; Yoganandan, Narayan; Maiman, Dennis J; Scarboro, Mark; Rudd, Rodney W

2012-01-01

There is currently no injury assessment for thoracic or lumbar spine fractures in the motor vehicle crash standards throughout the world. Compression-related thoracolumbar fractures are occurring in frontal impacts and yet the mechanism of injury is poorly understood. The objective of this investigation was to characterize these injuries using real world crash data from the US-DOT-NHTSA NASS-CDS and CIREN databases. Thoracic and lumbar AIS vertebral body fracture codes were searched for in the two databases. The NASS database was used to characterize population trends as a function of crash year and vehicle model year. The CIREN database was used to examine a case series in more detail. From the NASS database there were 2000-4000 occupants in frontal impacts with thoracic and lumbar vertebral body fractures per crash year. There was an increasing trend in incidence rate of thoracolumbar fractures in frontal impact crashes as a function of vehicle model year from 1986 to 2008; this was not the case for other crash types. From the CIREN database, the thoracolumbar spine was most commonly fractured at either the T12 or L1 level. Major, burst type fractures occurred predominantly at T12, L1 or L5; wedge fractures were most common at L1. Most CIREN occupants were belted; there were slightly more females involved; they were almost all in bucket seats; impact location occurred approximately half the time on the road and half off the road. The type of object struck also seemed to have some influence on fractured spine level, suggesting that the crash deceleration pulse may be influential in the type of compression vector that migrates up the spinal column. Future biomechanical studies are required to define mechanistically how these fractures are influenced by these many factors.

Radiologic study of disc behavior following compression fracture of the thoracolumbar hinge managed by kyphoplasty: A 52-case series.

PubMed

Teyssédou, S; Saget, M; Gayet, L E; Pries, P; Brèque, C; Vendeuvre, T

2016-02-01

Kyphoplasty has proved effective for durable correction of traumatic vertebral deformity following Magerl A fracture, but subsequent behavior of the adjacent discs is unclear. The objective of the present study was to analyze evolution according to severity of initial kyphosis and quality of fracture reduction. A single-center prospective study included cases of single compression fracture of the thoracolumbar hinge managed by Kyphon Balloon Kyphoplasty with polymethylmethacrylate bone cement. Radiology focused on traumatic vertebral kyphosis (VK), disc angulation (DA) and disc height index (DHI) in the adjacent discs. Linear regression assessed the correlation between superior disc height index (SupDHI) and postoperative VK on the one hand and correction gain on the other, using the Student t test for matched pairs and Pearson correlation coefficient. Fifty-two young patients were included, with mean follow-up of 18.6 months. VK fell from 13.9° preoperatively to 8.2° at last follow-up. DHI found significant superior disc subsidence (P=0.0001) and non-significant inferior disc subsidence (P=0.116). DA showed significantly reduced superior disc lordosis (P=4*10(-5)). SupDHI correlated with VK correction (r=0.32). Preoperative VK did not correlate with radiologic degeneration of the adjacent discs. Correction of traumatic vertebral deformity avoids subsidence and loss of mechanical function in the superior adjacent disc. The underlying disc compensates for residual deformity. Balloon kyphoplasty is useful in compression fracture, providing significant reduction of traumatic vertebral deformity while conserving free and healthy adjacent discs. IV. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Proximal Pole Scaphoid Nonunion Reconstruction With 1,2 Intercompartmental Supraretinacular Artery Vascularized Graft and Compression Screw Fixation.

PubMed

Morris, Mark S; Zhu, Andy F; Ozer, Kagan; Lawton, Jeffrey N

2018-02-06

To review the incidence of union of patients with proximal pole scaphoid fracture nonunions treated using a 1,2 intercompartmental supraretinacular artery (1,2 ICSRA) vascularized graft and a small compression screw. This is a retrospective case series of 12 patients. Calculations of the size of the proximal pole fragment relative to the total scaphoid were performed using posteroanterior view scaphoid radiographs with the wrist in ulnar deviation and flat on the cassette. Analyses were repeated 3 times per subject, and the average ratio of proximal pole fragment relative to the entire scaphoid was calculated. We reviewed medical records, radiographs, and computed tomography (CT) scans of these 12 patients. The CT scans that were performed after an average of 12 weeks were ultimately used to confirm union of the scaphoid fractures. One patient was unable to have a CT so was excluded from the final calculation. All 11 (100%) scaphoid fractures that were assessed by CT were found to be healed at the 12-week assessment point. The mean proximal pole fragment size was 18% (range, 7%-27%) of the entire scaphoid. The 1,2 ICSRA vascularized graft and compression screw was an effective treatment for patients with proximal pole scaphoid fractures. Therapeutic IV. Copyright © 2018 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Fracture, failure and compression behaviour of a 3D interconnected carbon aerogel (Aerographite) epoxy composite

DOE PAGES

Chandrasekaran, S.; Liebig, W. V.; Mecklenberg, M.; ...

2015-11-04

Aerographite (AG) is a mechanically robust, lightweight synthetic cellular material, which consists of a 3D interconnected network of tubular carbon [1]. The presence of open channels in AG aids to infiltrate them with polymer matrices, thereby yielding an electrical conducting and lightweight composite. Aerographite produced with densities in the range of 7–15 mg/cm 3 was infiltrated with a low viscous epoxy resin by means of vacuum infiltration technique. Detailed morphological and structural investigations on synthesized AG and AG/epoxy composite were performed by scanning electron microscopic techniques. Our present study investigates the fracture and failure of AG/epoxy composites and its energymore » absorption capacity under compression. The composites displayed an extended plateau region when uni-axially compressed, which led to an increase in energy absorption of ~133% per unit volume for 1.5 wt% of AG, when compared to pure epoxy. Preliminary results on fracture toughness showed an enhancement of ~19% in K IC for AG/epoxy composites with 0.45 wt% of AG. Furthermore, our observations of fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite failure as the dominating mechanism for the toughness improvement in these composites. These observations were consistent with the results obtained from photoelasticity experiments on a thin film AG/epoxy model composite.« less

Prediction of fracture healing under axial loading, shear loading and bending is possible using distortional and dilatational strains as determining mechanical stimuli.

PubMed

Steiner, Malte; Claes, Lutz; Ignatius, Anita; Niemeyer, Frank; Simon, Ulrich; Wehner, Tim

2013-09-06

Numerical models of secondary fracture healing are based on mechanoregulatory algorithms that use distortional strain alone or in combination with either dilatational strain or fluid velocity as determining stimuli for tissue differentiation and development. Comparison of these algorithms has previously suggested that healing processes under torsional rotational loading can only be properly simulated by considering fluid velocity and deviatoric strain as the regulatory stimuli. We hypothesize that sufficient calibration on uncertain input parameters will enhance our existing model, which uses distortional and dilatational strains as determining stimuli, to properly simulate fracture healing under various loading conditions including also torsional rotation. Therefore, we minimized the difference between numerically simulated and experimentally measured courses of interfragmentary movements of two axial compressive cases and two shear load cases (torsional and translational) by varying several input parameter values within their predefined bounds. The calibrated model was then qualitatively evaluated on the ability to predict physiological changes of spatial and temporal tissue distributions, based on respective in vivo data. Finally, we corroborated the model on five additional axial compressive and one asymmetrical bending load case. We conclude that our model, using distortional and dilatational strains as determining stimuli, is able to simulate fracture-healing processes not only under axial compression and torsional rotation but also under translational shear and asymmetrical bending loading conditions.

[Osteosynthesis of metacarpal fractures with 2.0 mm LCP system and functional postoperative treatment].

PubMed

Oberreiter, B; Kilgus, M; Bodmer, E; Platz, A

2017-01-01

Locking head systems are an additional option in the surgical treatment of metacarpal fractures. In this clinic 2.0 mm locking compression plates (LCP) are used, which provide the possibility of functional postoperative treatment even for complex and osteoporotic metacarpal fractures. For simple fractures and good bone quality the LCP system is used as a compression or neutralization plate. Depending on the type and localization of the fracture, different osteosynthesis techniques are used in order to achieve a functional postoperative treatment in as many patients as possible. Between July 2009 and December 2010 a total of 49 patients were enrolled in a prospective trial. All patients underwent surgical treatment with a 2.0 mm LCP system. Postoperative functionality of the hand was restored without immobilization. Clinical and radiological examinations were performed after 6 and 12 weeks and after 6 and 12 months with documentation of the range of motion (ROM), grip strength, fingertip to palm distance and the disabilities of the arm, shoulder and hand (DASH) score. After 6 months a good functional result was achieved in all patients with no cases of malrotation. Radiographs showed a completely consolidated bone healing. After osteosynthesis with 2.0 mm LCPs all types of metacarpal fractures can be treated without immobilization.

Generalized Fracture Toughness and Compressive Strength of Sustainable Concrete Including Low Calcium Fly Ash.

PubMed

Golewski, Grzegorz Ludwik

2017-12-06

The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters. The experiments were carried out after: 3, 7, 28, 90, 180 and 365 days of curing. Fracture toughness of concretes was determined in terms of the critical stress intensity factors: K I c S , K I I c , K I I I c and then a generalized fracture toughness K c was specified. The obtained results are significant for the analysis of concrete structures subjected to complex loading. The properties of composites with the additive of LCFA depend on the age of the concrete tested. Mature concretes exhibit high fracture toughness at 20% additive of LCFA, while the additive of LCFA in the amount of 30% weight of cement has a beneficial effect on the parameters of concrete only after half a year of curing.

Generalized Fracture Toughness and Compressive Strength of Sustainable Concrete Including Low Calcium Fly Ash

PubMed Central

2017-01-01

The paper presents the results of tests on the effect of the low calcium fly ash (LCFA) addition, in the amounts of: 0% (LCFA-00), 20% (LCFA-20) and 30% (LCFA-30) by weight of cement, on fracture processes in structural concretes. In the course of the experiments, compressive strength of concrete and fracture toughness for: I (tensile), II (in-plane shear) and III (anti-plane shear) models of cracking were measured. The tests determined the effect of age of concretes modified with LCFA on the analyzed parameters. The experiments were carried out after: 3, 7, 28, 90, 180 and 365 days of curing. Fracture toughness of concretes was determined in terms of the critical stress intensity factors: KIcS, KIIc, KIIIc and then a generalized fracture toughness Kc was specified. The obtained results are significant for the analysis of concrete structures subjected to complex loading. The properties of composites with the additive of LCFA depend on the age of the concrete tested. Mature concretes exhibit high fracture toughness at 20% additive of LCFA, while the additive of LCFA in the amount of 30% weight of cement has a beneficial effect on the parameters of concrete only after half a year of curing. PMID:29211029

Assessment of function-graded materials as fracture fixation bone-plates under combined loading conditions using finite element modelling.

PubMed

Fouad, H

2011-05-01

In previous work by Fouad (Medical Engineering and Physics 2010 [23]), 3D finite element (FE) models for fractured bones with function-graded (FG) bone-plates and traditional bone-plates made of stainless steel (SS) and titanium (Ti) alloy were examined under compressive loading conditions using the ABAQUS Code. In this study, the effects of the presence of the torsional load in addition to the compressive load on the predicted stresses of the fracture fixation bone-plate system are examined at different healing stages. The effects on the stress on the fracture site when using contacted and non-contacted bone-plate systems are also studied. The FE modelling results indicate that the torsional load has significant effects on the resultant stress on the fracture fixation bone-plate system, which should be taken into consideration during the design and the analysis. The results also show that the stress shielding at the fracture site decreases significantly when using FG bone-plates compared to Ti alloy or SS bone-plates. The presence of a gap between the bone and the plate results in a remarkable reduction in bone stress shielding at the fracture site. Therefore, the significant effects of using an FG bone-plate with a gap and the presence of torsional load on the resultant stress on the fracture fixation bone-plate system should be taken into consideration. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Outcome of locking compression plates in humeral shaft nonunions

PubMed Central

Kumar, Malhar N; Ravindranath, V Pratap; Ravishankar, MR

2013-01-01

Background: Nonunion of diaphyseal fractures of the humerus are frequently seen in clinical practice (incidence of up to 15% in certain studies) and osteosynthesis using dynamic compression plates, intra medullary nails and Ilizarov fixators have been reported previously. Locking compression plates (LCP) are useful in the presence of disuse osteoporosis, segmental bone loss and cortical defects that preclude strong fixation. We report a prospective followup study of the outcome of the use of LCP for humeral nonunion following failed internal fixation in which implants other than LCP had been used. Materials and Methods: Twenty four patients with nonunion of humeral shaft fractures following failed internal fixation were included in the study. The mean followup period was 3.4 years (range: 2.4 to 5.7 years) and the minimum followup period was 2 years. Mean age of the patients was 41.04 years (range: 24 to 57 years). All 24 patients underwent osteosynthesis using LCP and autologous bone grafting (cortico-cancellous iliac crest graft combined with or without fibular strut graft). Main outcome measurements included radiographic assessment of fracture union and pre and postoperative functional evaluation using the modified Constant and Murley scoring system. Results: 23 out of 24 fractures united following osteosynthesis. Average time to union was 16 weeks (range: 10 to 28 weeks). Complications included delayed union (n = 2), transient radial nerve palsy (n = 2) and persistent nonunion (n = 1). Functional evaluation using the Constant and Murley score showed excellent results in 11, good in 10, fair in two and poor outcome in one patient. Conclusions: Locking compression plating and cancellous bone grafting is a reliable option for achieving union in humeral diaphyseal nonunion with failed previous internal fixation and results in good functional outcome in patients with higher physiological demands. PMID:23682176

Compress knee arthroplasty has 80% 10-year survivorship and novel forms of bone failure.

PubMed

Healey, John H; Morris, Carol D; Athanasian, Edward A; Boland, Patrick J

2013-03-01

Compliant, self-adjusting compression technology is a novel approach for durable prosthetic fixation of the knee. However, the long-term survival of these constructs is unknown. We therefore determined the survival of the Compress prosthesis (Biomet Inc, Warsaw, IN, USA) at 5 and 10 actuarial years and identified the failure modes for this form of prosthetic fixation. We retrospectively reviewed clinical and radiographic records for all 82 patients who underwent Compress knee arthroplasty from 1998 to 2008, as well as one patient who received the device elsewhere but was followed at our institution. Prosthesis survivorship and modes of failure were determined. Followup was for a minimum of 12 months or until implant removal (median, 43 months; range, 6-131 months); 28 patients were followed for more than 5 years. We found a survivorship of 85% at 5 years and 80% at 10 years. Eight patients required prosthetic revision after interface failure due to aseptic loosening alone (n = 3) or aseptic loosening with periprosthetic fracture (n = 5). Additionally, five periprosthetic bone failures occurred that did not require revision: three patients had periprosthetic bone failure without fixation compromise and two exhibited irregular prosthetic osteointegration patterns with concomitant fracture due to mechanical insufficiency. Compress prosthetic fixation after distal femoral tumor resection exhibits long-term survivorship. Implant failure was associated with patient nonadherence to the recommended weightbearing proscription or with bone necrosis and fracture. We conclude this is the most durable FDA-approved fixation method for distal femoral megaprostheses. Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

A novel fixation system for sacroiliac dislocation fracture: internal fixation system design and biomechanics analysis.

PubMed

Dawei, Tian; Na, Liu; Jun, Lei; Wei, Jin; Lin, Cai

2013-02-01

Although there were many different types of fixation techniques for sacroiliac dislocation fracture, the treat remained challenging in posterior pelvic ring injury. The purpose of this study was to evaluate the biomechanical effects of a novel fixation system we designed. 12 human cadavers (L3-pelvic-femora) were used to compare biomechanical stability after reconstruction on the same specimens in four conditions: (1) intact, (2) cable system, (3) plate-pedicle screw system, and (4) cable system and plate-pedicle screw combination system (combination system). Biomechanical testing was performed on a material testing machine for evaluating the stiffness of the pelvic fixation construct in compression and torsion. The cable system and plate-pedicle screw system alone may be insufficient to resist vertical shearing and rotational loads; however the combination system for unstable sacroiliac dislocation fractures provided significantly greater stability than single plate-pedicle or cable fixation system. The novel fixation system for unstable sacroiliac dislocation fractures produced sufficient stability in axial compression and axial rotation test in type C pelvic ring injuries. It may also offer a better solution for sacroiliac dislocation fractures. Copyright © 2012 Elsevier Ltd. All rights reserved.

Impact of Stress on Anomalous Transport in Fractured Rock

NASA Astrophysics Data System (ADS)

Kang, P. K.; Lei, Q.; Lee, S.; Dentz, M.; Juanes, R.

2016-12-01

Fluid flow and transport in fractured rock controls many natural and engineered processes in the subsurface. However, characterizing flow and transport through fractured media is challenging due to the large heterogeneity of fractured rock properties. In addition to these "static" challenges, geologic fractures are always under significant overburden stress, and changes in the stress state can lead to changes in the fracture's ability to conduct fluids. While confining stress has been shown to impact fluid flow through fractures in a fundamental way, the impact of confining stress on transport through fractured rock remains largely unexplored. The link between anomalous (non-Fickian) transport and confining stress has been shown only recently, at the level of a single rough fracture [1]. Here, we investigate the impact of confining stress on flow and transport through discrete fracture networks. We model geomechanical effects in 2D fractured rock by means of a finite-discrete element method (FEMDEM), which can capture the deformation of matrix blocks, reactivation and propagation of cracks. We implement a joint constitutive model within the FEMDEM framework to simulate the effect of fracture roughness. We apply the model to a fracture network extracted from the geological map of an actual outcrop to obtain the aperture field at different stress conditions (Figure 1). We then simulate fluid flow and particle transport through the stressed fracture networks. We observe that anomalous transport emerges in response to confining stress on the fracture networks, and show that this anomalous behavior can be linked to the stress state of the rock. Finally, we develop an effective transport model that captures the anomalous transport through stressed fractures. Our results point to a heretofore unrecognized link between geomechanics and anomalous transport in discrete fractured networks. [1] P. K. Kang, S. Brown, and R. Juanes, Emergence of anomalous transport in stressed rough fractures. Earth and Planetary Science Letters, to appear (2016). Figure (a) Map of maximum principal stress with a vertical normal compressive stress of 3 MPa at top and bottom boundaries, and 1MPa at left and right boundaries. (b) Normal compressive stress of 15 MPa at top and bottom boundaries, and 5MPa at left and right boundaries.

The influence of impact direction and axial loading on the bone fracture pattern.

PubMed

Cohen, Haim; Kugel, Chen; May, Hila; Medlej, Bahaa; Stein, Dan; Slon, Viviane; Brosh, Tamar; Hershkovitz, Israel

2017-08-01

The effect of the direction of the impact and the presence of axial loading on fracture patterns have not yet been established in experimental 3-point bending studies. To reveal the association between the direction of the force and the fracture pattern, with and without axial loading. A Dynatup Model POE 2000 (Instron Co.) low energy pendulum impact machine was utilized to apply impact loading on fresh pig femoral bones (n=50). The bone clamp shaft was adjusted to position the bone for three-point bending with and without additional bone compression. Four different directions of the force were applied: anterior, posterior, lateral, and medial. The impacted aspect can be distinguished from the non-impacted aspects based on the fracture pattern alone (the most fractured one); the impact point can be identified on bare bones (the area from which all oblique lines radiate and/or the presence of a chip fragment). None of our experiments (with and without compression) yielded a "true" butterfly fracture, but instead, oblique radiating lines emerged from the point of impact (also known as "false" butterfly). Impacts on the lateral and anterior aspects of the bones produce more and longer fracture lines than impacts on the contralateral side; bones subjected to an impact with axial loading are significantly more comminuted and fragmented. Under axial loading, the number of fracture lines is independent of the impact direction. Our study presents an experimental model for fracture analysis and shows that the impact direction and the presence of axial loading during impact significantly affect the fracture pattern obtained. Copyright © 2017 Elsevier B.V. All rights reserved.

Post-fatigue fracture resistance of metal core crowns: press-on metal ceramic versus a conventional veneering system

PubMed Central

Agustín-Panadero, Rubén; Campos-Estellés, Carlos; Labaig-Rueda, Carlos

2015-01-01

Background The aim of this in vitro study was to compare the mechanical failure behavior and to analyze fracture characteristics of metal ceramic crowns with two veneering systems – press-on metal (PoM) ceramic versus a conventional veneering system – subjected to static compressive loading. Material and Methods Forty-six crowns were constructed and divided into two groups according to porcelain veneer manufacture. Group A: 23 metal copings with porcelain IPS-InLine veneering (conventional metal ceramic). Group B: 23 metal copings with IPS-InLine PoM veneering porcelain. After 120,000 fatigue cycles, the crowns were axially loaded to the moment of fracture with a universal testing machine. The fractured specimens were examined under optical stereomicroscopy and scanning electron microscope. Results Fracture resistance values showed statistically significant differences (Student’s t-test) regarding the type of ceramic veneering technique (p=0.001): Group A (conventional metal ceramics) obtained a mean fracture resistance of 1933.17 N, and Group B 1325.74N (Press-on metal ceramics). The most common type of fracture was adhesive failure (with metal exposure) (p=0.000). Veneer porcelain fractured on the occlusal surface following a radial pattern. Conclusions Metal ceramic crowns made of IPS InLine or IPS InLine PoM ceramics with different laboratory techniques all achieved above-average values for clinical survival in the oral environment according to ISO 6872. Crowns made with IPS InLine by conventional technique resisted fracture an average of 45% more than IPS InLine PoM fabricated with the press-on technique. Key words:Mechanical failure, conventional feldspathic, pressable ceramic, chewing simulator, thermocycling, compressive testing, fracture types, scanning electron microscope. PMID:26155346

Management of distal humeral coronal shear fractures

PubMed Central

Yari, Shahram S; Bowers, Nathan L; Craig, Miguel A; Reichel, Lee M

2015-01-01

Coronal shear fractures of the distal humerus are rare, complex fractures that can be technically challenging to manage. They usually result from a low-energy fall and direct compression of the distal humerus by the radial head in a hyper-extended or semi-flexed elbow or from spontaneous reduction of a posterolateral subluxation or dislocation. Due to the small number of soft tissue attachments at this site, almost all of these fractures are displaced. The incidence of distal humeral coronal shear fractures is higher among women because of the higher rate of osteoporosis in women and the difference in carrying angle between men and women. Distal humeral coronal shear fractures may occur in isolation, may be part of a complex elbow injury, or may be associated with injuries proximal or distal to the elbow. An associated lateral collateral ligament injury is seen in up to 40% and an associated radial head fracture is seen in up to 30% of these fractures. Given the complex nature of distal humeral coronal shear fractures, there is preference for operative management. Operative fixation leads to stable anatomic reduction, restores articular congruity, and allows initiation of early range-of-motion movements in the majority of cases. Several surgical exposure and fixation techniques are available to reconstruct the articular surface following distal humeral coronal shear fractures. The lateral extensile approach and fixation with countersunk headless compression screws placed in an anterior-to-posterior fashion are commonly used. We have found a two-incision approach (direct anterior and lateral) that results in less soft tissue dissection and better outcomes than the lateral extensile approach in our experience. Stiffness, pain, articular incongruity, arthritis, and ulnohumeral instability may result if reduction is non-anatomic or if fixation fails. PMID:25984515

Trabecular fracture zone might not be the higher strain region of the trabecular framework

NASA Astrophysics Data System (ADS)

Tassani, Simone; Pani, Martino; Noailly, Jerome; Gonzalez Ballester, Miguel Angel

2018-02-01

Trabecular bone fracture is a traumatic and localized event studied worldwide in order to predict it. During the years researchers focussed over the mechanical characterization of the trabecular tissue to understand its mechanics. Several studies pointed out the very local nature of the trabecular failure, finally identifying the fracture zone with the aim to study it separately. The complexity of the three-dimensional trabecular framework and the local nature of the fracture event do not allow the direct evaluation of a single trabecula’s behaviour within its natural environment. For this reason, micro-Finite Element Modelling have been seen as the best way to investigate this biomechanical issue. Mechanical strain analysis is adopted in the literature for the identification of micro fracture using criteria based on principal strains. However, it was never verified if the fracture zone is actually the zone where principal strains are concentrated. Here we show how the maximum strain of the tissue might not be directly correlated to the fracture. In the present work a previously validated technique was used to identify the fracture zone of 10 trabecular specimen mechanically tested in compression and scanned in micro-CT before and after the mechanical test. Before-compression datasets were used to develop 10 micro-FE models were the same boundary conditions of the mechanical test were reproduced. Our results show how the known linear behaviour of the trabecular framework might not be directly related to the development of the fracture suggesting other non-linear phenomenon, like buckling or micro-damage, as actual cause of the traumatic event. This result might have several implications both in micro-modelling and in clinical applications for the study of fracture related pathology, like osteoporosis.

Surgical correction of severe strabismus and enophthalmos secondary to zygomatic arch fracture in a dog.

PubMed

Konrade, Kricket A; Clode, Alison B; Michau, Tammy M; Roe, Simon C; Trumpatori, Brian J; Krug, William V; Gilger, Brian C

2009-01-01

A grossly displaced segmental zygomatic arch fracture with marked ventro-lateral deviation of the left globe was diagnosed in a 3-month-old male German Shepherd dog following a bite injury. The fracture was approached via a modified lateral orbitotomy and a fragment of the lacrimal bone removed. The rostral portion of the fracture was stabilized with a 5-hole 2.0 dynamic compression plate bone plate. The surgical correction achieved sufficient skeletal fixation for proper anatomical reduction of the globe and excellent cosmetic and functional outcomes.

Operative treatment of sternal fractures.

PubMed

Al-Qudah, Abdullah

2006-10-01

Four patients with displaced sternal fractures complained of intractable pain following road traffic accidents. They all had bone deformities, but only one had associated traumatic injuries. All patients underwent operative reduction and fixation of the fractured sternum using a T-shaped compression-tension stainless steel plate and screws. Pain relief was often dramatic and all patients progressed to sternal union. None required reoperation. No infections occurred. Two plates have subsequently been removed. On follow-up, all patients had excellent results. Sternal plating, which is based on the tension-band principle, is an effective treatment for displaced sternal fractures.

Occipital Neuralgia after Occipital Cervical Fusion to Treat an Unstable Jefferson Fracture

PubMed Central

Kong, Seong Ju; Park, Jin Hoon

2012-01-01

In this report we describe a patient with an unstable Jefferson fracture who was treated by occipitocervical fusion and later reported sustained postoperative occipital neuralgia. A 70-year-old male was admitted to our center with a Jefferson fracture induced by a car accident. Preoperative lateral X-ray revealed an atlanto-dens interval of 4.8mm and a C1 canal anterior-posterior diameter of 19.94mm. We performed fusion surgery from the occiput to C5 without decompression of C1. The patient reported sustained continuous pain throughout the following year despite strong analgesics. The pain dermatome was located mainly in the great occipital nerve territory and posterior neck. Magnetic resonance images revealed no evidence of cord compression, however a C1 lamina compressed dural sac and C2 root compression could not be excluded. We performed bilateral C2 root decompression via a C1 laminectomy. After decompression, bilateral C2 root redundancy was identified by palpation. After decompression surgery, pain was reduced. This case indicates that occipital neuralgia, suggesting the need for diagnostic block, should be considered in the differential diagnosis of patients with sustained occipital headache after occipitocervical fusion surgery. PMID:25983846

Hydraulic fracture and resilience of epithelial monolayers under stretch

NASA Astrophysics Data System (ADS)

Arroyo, Marino; Lucantonio, Alessandro; Noselli, Giovanni; Casares, Laura; Desimone, Antonio; Trepat, Xavier

Epithelial monolayers are very simple and prevalent tissues. Their functions include delimiting distinct physicochemical containers and protecting us from pathogens. Epithelial fracture disrupts the mechanical integrity of this barrier, and hence compromises these functions. Here, we show that in addition to the conventional fracture resulting from excessive tissue tension, epithelia can hydraulically fracture under stretch as a result of the poroelastic nature of the matrix. We will provide experimental evidence of this counterintuitive mechanism of fracture, in which cracks appear under compression. Intriguingly, unlike tensional fracture, which is localized and catastrophic, hydraulic epithelial fracture is distributed and reversible. We will also describe the active mechanisms responsible for crack healing, and the physical principles by which the poroelastic matrix contributes to this resilient behavior.

Coupled Fracture and Flow in Shale in Hydraulic Fracturing

NASA Astrophysics Data System (ADS)

Carey, J. W.; Mori, H.; Viswanathan, H.

2014-12-01

Production of hydrocarbon from shale requires creation and maintenance of fracture permeability in an otherwise impermeable shale matrix. In this study, we use a combination of triaxial coreflood experiments and x-ray tomography characterization to investigate the fracture-permeability behavior of Utica shale at in situ reservoir conditions (25-50 oC and 35-120 bars). Initially impermeable shale core was placed between flat anvils (compression) or between split anvils (pure shear) and loaded until failure in the triaxial device. Permeability was monitored continuously during this process. Significant deformation (>1%) was required to generate a transmissive fracture system. Permeability generally peaked at the point of a distinct failure event and then dropped by a factor of 2-6 when the system returned to hydrostatic failure. Permeability was very small in compression experiments (< 1 mD), possibly because of limited fracture connectivity through the anvils. In pure share experiments, shale with bedding planes perpendicular to shear loading developed complex fracture networks with narrow apertures and peak permeability of 30 mD. Shale with bedding planes parallel to shear loading developed simple fractures with large apertures and a peak permeability as high as 1 D. Fracture systems held at static conditions for periods of several hours showed little change in effective permeability at hydrostatic conditions as high as 140 bars. However, permeability of fractured systems was a function of hydrostatic pressure, declining in a pseudo-linear, exponential fashion as pressure increased. We also observed that permeability decreased with increasing fluid flow rate indicating that flow did not follow Darcy's Law, possibly due to non-laminar flow conditions, and conformed to Forscheimer's law. The coupled deformation and flow behavior of Utica shale, particularly the large deformation required to initiate flow, indicates the probable importance of activation of existing fractures in hydraulic fracturing and that these fractures can have adequate permeability for the production of hydrocarbon.

The association between type of spine fracture and the mechanism of trauma: A useful tool for identifying mechanism of trauma on legal medicine field.

PubMed

Aghakhani, Kamran; Kordrostami, Roya; Memarian, Azadeh; Asl, Nahid Dadashzadeh; Zavareh, Fatemeh Noorian

2018-05-01

Determining the association between mechanism of trauma, and the type of spine column fracture is a useful approach for exactly describing spine injury on forensic medicine field. We aimed to determine mechanism of trauma based on distribution of the transition of spinal column fractures. This cross-sectional survey was performed on 117 consecutive patients with the history of spinal trauma who were admitted to emergency ward of Rasoul-e-Akram Hospital in Tehran, Iran from April 2015 to March 2016. The baseline characteristics were collected by reviewing the hospital recorded files. With respect to mechanism of fracture, 63.2% of fractures were caused by falling, 30.8% by collisions with motor vehicles, and others caused by the violence. Regarding site of fracture, lumbosacral was affected in 47.9%, thoracic in 29.9%, and cervical in 13.7%. Regarding type of fracture, burst fracture was the most common type (71.8%) followed by compressive fracture (14.5%). The site of fracture was specifically associated with the mechanism of injury; the most common injuries induced by falling from height were found in lumbosacral and cervical sites, and the most frequent injuries by traffic accidents were found in thoracic site; also the injuries following violence were observed more in lumbar vertebrae. The burst fractures were more revealed in the patients affected by falling from height and by traffic accidents, and both burst and compressive fractures were more observed with the same result in the patients injured with violence (p = 0.003). The type of spine fracture due to trauma is closely associated with the mechanism of trauma that can be helpful in legal medicine to identify the mechanism of trauma in affected patients. Copyright © 2018. Published by Elsevier Ltd.

Stress-Shielding Effect of Nitinol Swan-Like Memory Compressive Connector on Fracture Healing of Upper Limb

NASA Astrophysics Data System (ADS)

Fu, Q. G.; Liu, X. W.; Xu, S. G.; Li, M.; Zhang, C. C.

2009-08-01

In this article, the stress-shielding effect of a Nitinol swan-like memory compressive connector (SMC) is evaluated. Patients with fracture healing of an upper limb after SMC internal fixation or stainless steel plate fixation were randomly selected and observed comparatively. With the informed consent of the SMC group, minimal cortical bone under the swan-body and swan-neck was harvested; and in the steel plate fixation group, minimal cortical bone under the steel plate and opposite side to the steel plate was also harvested for observation. Main outcome measurements were taken such as osteocyte morphology, Harversian canal histological observation under light microscope; radiographic observation of fracture healing, and computed tomography quantitative scanning of cortical bone. As a conclusion, SMC has a lesser stress-shielding effect to fixed bone than steel plate. Finally, the mechanism of the lesser stress-shielding effect of SMC is discussed.

Effect of Growth Rate on Elevated Temperature Plastic Flow and Room Temperature Fracture Toughness of Directionally Solidified NiAl-31Cr-3Mo

NASA Technical Reports Server (NTRS)

Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.; Salem, J. A.

1999-01-01

The eutectic system Ni-33Al-31Cr-3Mo was directionally solidified at rates ranging from 7.6 to 508 mm/h. Samples were examined for microstructure and alloy chemistry, compression tested at 1200 and 1300 K, and subjected to room temperature fracture toughness measurements. Lamellar eutectic grains were formed at 12.7 mm/h; however cellular structures with a radial eutectic pattern developed at faster growth rates. Elevated temperature compression testing between 10(exp -4) to 10(exp -7)/s did not reveal an optimum growth condition, nor did any single growth condition result in a significant fracture toughness advantage. The mechanical behavior, taken together, suggests that Ni-33Al-31Cr-3Mo grown at rates from 25.4 to 254 mm/h will have nominally equivalent properties.

Modelling deformation and fracture in confectionery wafers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohammed, Idris K.; Charalambides, Maria N.; Williams, J. Gordon

2015-01-22

The aim of this research is to model the deformation and fracture behaviour of brittle wafers often used in chocolate confectionary products. Three point bending and compression experiments were performed on beam and circular disc samples respectively to determine the 'apparent' stress-strain curves in bending and compression. The deformation of the wafer for both these testing types was observed in-situ within an SEM. The wafer is modeled analytically and numerically as a composite material with a core which is more porous than the skins. X-ray tomography was used to generate a three dimensional volume of the wafer microstructure which wasmore » then meshed and used for quantitative analysis. A linear elastic material model, with a damage function and element deletion, was used and the XMT generated architecture was loaded in compression. The output from the FE simulations correlates closely to the load-deflection deformation observed experimentally.« less

Modelling deformation and fracture in confectionery wafers

NASA Astrophysics Data System (ADS)

Mohammed, Idris K.; Charalambides, Maria N.; Williams, J. Gordon; Rasburn, John

2015-01-01

The aim of this research is to model the deformation and fracture behaviour of brittle wafers often used in chocolate confectionary products. Three point bending and compression experiments were performed on beam and circular disc samples respectively to determine the 'apparent' stress-strain curves in bending and compression. The deformation of the wafer for both these testing types was observed in-situ within an SEM. The wafer is modeled analytically and numerically as a composite material with a core which is more porous than the skins. X-ray tomography was used to generate a three dimensional volume of the wafer microstructure which was then meshed and used for quantitative analysis. A linear elastic material model, with a damage function and element deletion, was used and the XMT generated architecture was loaded in compression. The output from the FE simulations correlates closely to the load-deflection deformation observed experimentally.

Bending fracture in carbon nanotubes.

PubMed

Kuo, Wen-Shyong; Lu, Hsin-Fang

2008-12-10

A novel approach was adopted to incur bending fracture in carbon nanotubes (CNTs). Expanded graphite (EG) was made by intercalating and exfoliating natural graphite flakes. The EG was deposited with nickel particles, from which CNTs were grown by chemical vapor deposition. The CNTs were tip-grown, and their roots were fixed on the EG flakes. The EG flakes were compressed, and many CNTs on the surface were fragmented due to the compression-induced bending. Two major modes of the bending fracture were observed: cone-shaped and shear-cut. High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the crack growth within the graphene layers. The bending fracture is characterized by two-region crack growth. An opening crack first appears around the outer-tube due to the bending-induced tensile stress. The crack then branches to grow along an inclined direction toward the inner-tube due to the presence of the shear stress in between graphene layers. An inner-tube pullout with inclined side surface is formed. The onset and development of the crack in these two regions are discussed.

Effect of cooling rates on the structure, density and micro-indentation behavior of the Fe, Co-based bulk metallic glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lesz, Sabina, E-mail: sabina.lesz@polsl.pl

The experiments demonstrate that ductility of the samples of bulk metallic glass (BMG) with the same chemical composition increased with decreasing sample size. It is shown that microhardness and density increases with decreasing the cooling rate. The fracture morphology of rods after compressive fracture were different on the cross section. Two characteristic features of the compressive fracture morphologies of metallic glasses (MGs) were observed in samples: smooth region and the vein pattern. Many parallel shear bands were observed on the deformed specimen with ϕ = 2 mm in diameter. The results provide more understanding on the relationship among the coolingmore » rate, structure and micro-indentation behavior of the Fe-Co-based BMGs. - Highlights: •Fracture morphology and micro-indentation behavior is studied. •The smaller BMG sample exhibits the larger plasticity. •Microhardness and density increase with decreasing the cooling rate. •Formation of shear bands has been reported in deformed specimens. •Structure and mechanical properties of BMGs can be controlled by the cooling rate.« less

Response of resin transfer molded (RTM) composites under reversed cyclic loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahfuz, H.; Haque, A.; Yu, D.

1996-01-01

Compressive behavior and the tension-compression fatigue response of resin transfer molded IM7 PW/PR 500 composite laminate with a circular notch have been studied. Fatigue damage characteristics have been investigated through the changes in the laminate strength and stiffness by gradually incrementing the fatigue cycles at a preselected load level. Progressive damage in the surface of the laminate during fatigue has been investigated using cellulose replicas. Failure mechanisms during static and cyclic tests have been identified and presented in detail. Extensive debonding of filaments and complete fiber bundle fracture accompanied by delamination were found to be responsible for fatigue failures, whilemore » fiber buckling, partial fiber fracture and delamination were characterized as the failure modes during static tests. Weibull analysis of the static, cyclic and residual tests have been performed and described in detail. Fractured as well as untested specimens were C-scanned, and the progressive damage growth during fatigue is presented. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) for the fractured specimen were also performed and the analysis of the failure behavior is presented.« less

Dynamic fracture of sintered Nd-Fe-B magnet under uniaxial compression

NASA Astrophysics Data System (ADS)

Wang, Huanran; Wan, Yin; Chen, Danian; Lei, Guohua; Ren, Chunying

2018-06-01

The dynamic fracture of the Nd-Fe-B magnets under uniaxial compression is investigated using a split Hopkinson pressure bar (SHPB). The surface deformation and fracture processes of the Nd-Fe-B specimens are recorded adopting a high-speed photography (HSP) with digital image correlation (DIC). The load and work applied to the specimens in the SHPB tests are determined with the strain signals of the transmitted and reflected waves. The surface strain distributions of the Nd-Fe-B specimen during the SHPB testing are revealed with DIC. It is shown by the HSP with DIC that when the load is near the maximum, the cracks at some positions on the surface of the expanding Nd-Fe-B specimen are formed and ran along certain directions. The work applied to the specimen per unit volume which corresponds to the maximal load is used to characterize the impact stability of the Nd-Fe-B specimen. The localized fracture strains at some positions on the surface of the expanding specimens at some characteristic times are determined with DIC, which are the projections of the strains onto the DIC plane.

The Effect of Loading Rate on Hydraulic Fracturing in Synthetic Granite - a Discrete Element Study

NASA Astrophysics Data System (ADS)

Tomac, I.; Gutierrez, M.

2015-12-01

Hydraulic fracture initiation and propagation from a borehole in hard synthetic rock is modeled using the two dimensional Discrete Element Method (DEM). DEM uses previously established procedure for modeling the strength and deformation parameters of quasi-brittle rocks with the Bonded Particle Model (Itasca, 2004). A series of simulations of laboratory tests on granite in DEM serve as a reference for synthetic rock behavior. Fracturing is enabled by breaking parallel bonds between DEM particles as a result of the local stress state. Subsequent bond breakage induces fracture propagation during a time-stepping procedure. Hydraulic fracturing occurs when pressurized fluid induces hoop stresses around the wellbore which cause rock fracturing and serves for geo-reservoir permeability enhancement in oil, gas and geothermal industries. In DEM, a network of fluid pipes and reservoirs is used for mathematical calculation of fluid flow through narrow channels between DEM particles, where the hydro-mechanical coupling is fully enabled. The fluid flow calculation is superimposed with DEM stress-strain calculation at each time step. As a result, the fluid pressures during borehole pressurization in hydraulic fracturing, as well as, during the fracture propagation from the borehole, can be simulated. The objective of this study is to investigate numerically a hypothesis that fluid pressurization rate, or the fluid flow rate, influences upon character, shape and velocity of fracture propagation in rock. The second objective is to better understand and define constraints which are important for successful fracture propagation in quasi-brittle rock from the perspective of flow rate, fluid density, viscosity and compressibility relative to the rock physical properties. Results from this study indicate that not only too high fluid flow rates cause fracture arrest and multiple fracture branching from the borehole, but also that the relative compressibility of fracturing fluid and rock plays a significant role in fracture propagation velocity. Fluid viscosity effects are similar to the loading rate effects, because in both cases the rapid buildup of the pressure in the wellbore in absence of the inflow of the fluid into initiated fracture causes induction of multiple simultaneous fracture branches at the wellbore wall.

Cement Leakage in Percutaneous Vertebral Augmentation for Osteoporotic Vertebral Compression Fractures: Analysis of Risk Factors.

PubMed

Xie, Weixing; Jin, Daxiang; Ma, Hui; Ding, Jinyong; Xu, Jixi; Zhang, Shuncong; Liang, De

2016-05-01

The risk factors for cement leakage were retrospectively reviewed in 192 patients who underwent percutaneous vertebral augmentation (PVA). To discuss the factors related to the cement leakage in PVA procedure for the treatment of osteoporotic vertebral compression fractures. PVA is widely applied for the treatment of osteoporotic vertebral fractures. Cement leakage is a major complication of this procedure. The risk factors for cement leakage were controversial. A retrospective review of 192 patients who underwent PVA was conducted. The following data were recorded: age, sex, bone density, number of fractured vertebrae before surgery, number of treated vertebrae, severity of the treated vertebrae, operative approach, volume of injected bone cement, preoperative vertebral compression ratio, preoperative local kyphosis angle, intraosseous clefts, preoperative vertebral cortical bone defect, and ratio and type of cement leakage. To study the correlation between each factor and cement leakage ratio, bivariate regression analysis was employed to perform univariate analysis, whereas multivariate linear regression analysis was employed to perform multivariate analysis. The study included 192 patients (282 treated vertebrae), and cement leakage occurred in 100 vertebrae (35.46%). The vertebrae with preoperative cortical bone defects generally exhibited higher cement leakage ratio, and the leakage is typically type C. Vertebrae with intact cortical bones before the procedure tend to experience type S leakage. Univariate analysis showed that patient age, bone density, number of fractured vertebrae before surgery, and vertebral cortical bone were associated with cement leakage ratio (P<0.05). Multivariate analysis showed that the main factors influencing bone cement leakage are bone density and vertebral cortical bone defect, with standardized partial regression coefficients of -0.085 and 0.144, respectively. High bone density and vertebral cortical bone defect are independent risk factors associated with bone cement leakage.

Open Screw Placement in a 1.5 mm LCP Over a Fracture Gap Decreases Fatigue Life

PubMed Central

Alwen, Sarah G. J.; Kapatkin, Amy S.; Garcia, Tanya C.; Milgram, Joshua; Stover, Susan M.

2018-01-01

Objective To investigate the influence of plate and screw hole position on the stability of simulated radial fractures stabilized with a 1.5 mm condylar locking compression plate (LCP). Study Design In vitro mechanical testing of paired cadaveric limbs. Sample Population Paired radii (n = 7) stabilized with a 1.5 mm condylar LCP with an open screw hole positioned either proximal to (PG), or over (OG), a simulated small fracture gap. Methods Constructs were cycled in axial compression at a simulated trot load until failure or a maximum of 200,000 cycles. Specimens that sustained 200,000 cycles without failure were then loaded in axial compression in a single cycle to failure. Construct cyclic axial stiffness and gap strain, fatigue life, and residual strength were evaluated and compared between constructs using analysis of variance. Results Of pairs that had a failure during cyclic loading, OG constructs survived fewer cycles (54,700 ± 60,600) than PG (116,800 ± 49,300). OG constructs had significantly lower initial stiffness throughout cyclic loading and higher gap strain range within the first 1,000 cycles than PG constructs. Residual strength variables were not significantly different between constructs, however yield loads occurred at loads only marginally higher than approximated trot loads. Fatigue life decreased with increasing body weight. Conclusion Fracture fixation stability is compromised by an open screw hole directly over a fracture gap compared to the open screw hole being buttressed by bone in the model studied. The 1.5 mm condylar LCP may be insufficient stabilization in dogs with appropriate radial geometry but high body weights. PMID:29876361

Resistance to compression of weakened roots subjected to different root reconstruction protocols

PubMed Central

ZOGHEIB, Lucas Villaça; SAAVEDRA, Guilherme de Siqueira Ferreira Anzaloni; CARDOSO, Paula Elaine; VALERA, Márcia Carneiro; de ARAÚJO, Maria Amélia Máximo

2011-01-01

Objective This study evaluated, in vitro, the fracture resistance of human non-vital teeth restored with different reconstruction protocols. Material and methods Forty human anterior roots of similar shape and dimensions were assigned to four groups (n=10), according to the root reconstruction protocol: Group I (control): non-weakened roots with glass fiber post; Group II: roots with composite resin by incremental technique and glass fiber post; Group III: roots with accessory glass fiber posts and glass fiber post; and Group IV: roots with anatomic glass fiber post technique. Following post cementation and core reconstruction, the roots were embedded in chemically activated acrylic resin and submitted to fracture resistance testing, with a compressive load at an angle of 45º in relation to the long axis of the root at a speed of 0.5 mm/min until fracture. All data were statistically analyzed with bilateral Dunnett's test (α=0.05). Results Group I presented higher mean values of fracture resistance when compared with the three experimental groups, which, in turn, presented similar resistance to fracture among each other. None of the techniques of root reconstruction with intraradicular posts improved root strength, and the incremental technique was suggested as being the most recommendable, since the type of fracture that occurred allowed the remaining dental structure to be repaired. Conclusion The results of this in vitro study suggest that the healthy remaining radicular dentin is more important to increase fracture resistance than the root reconstruction protocol. PMID:22231002

Finite element analysis of locking plate and two types of intramedullary nails for treating mid-shaft clavicle fractures.

PubMed

Ni, Ming; Niu, Wenxin; Wong, Duo Wai-Chi; Zeng, Wei; Mei, Jiong; Zhang, Ming

2016-08-01

Both plate and intramedullary nail fixations, including straight and anatomic nails, have been clinically adopted for the treatment of displaced mid-shaft clavicle fractures. However, the biomechanical performances of these fixations and implants have not been well evaluated. This study aims to compare the construct stability, stress distribution and fracture micro-motion of three fixations based on finite element (FE) method. The FE model of clavicle was reconstructed from CT images of a male volunteer. A mid-shaft fracture gap was created in the intact clavicle. Three fixation styles were simulated including locking plate (LP), anatomic intramedullary nail (CRx), and straight intramedullary nail (RCP). Two loading scenarios (axial compression and inferior bending) were applied at the distal end of the clavicle to simulate arm abduction, while the sternal end was fixed. Under both conditions, the LP was the stiffest, followed by the CRx, and the RCP was the weakest. LP also displayed a more evenly stress distribution for both implant and bone. RCP had a higher stress compared with CRx in both conditions. Moreover, all implants sustained higher stress level under the loading condition of bending than compression. The plate fixation significantly stabilizes the fracture gap, reduces the implant stress, and serves as the recommended fixation for the mid-shaft clavicle fracture. The CRx is an alternative device to treat clavicle shaft fracture, but the shoulder excessive activities should be avoided after operation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Characterization of Sheet Fracture Patterns in Polygonal-Jointed Lavas at Kokostick Butte, OR, and Mazama Ridge, WA: Investigation and Interpretation of Their Formation and Significance

NASA Astrophysics Data System (ADS)

Lodge, R. W.; Lescinsky, D. T.

2006-12-01

Polygonal joints in lava flows ("columns") are commonly equant leading to a model of formation associated with cooling in an isotropic stress field. This model, however, does not explain rectangular columns, sheet-like fractures, fractures with crosscutting relationships, and fractures with orientations other than perpendicular to the cooling surface. These fracture patterns are often observed at glaciated volcanoes. The presence of preferential fracture orientations suggests an applied stress component likely due to environmental conditions such as the presence of glaciers or flow dynamics such as down-slope settling or flow margin inflation. During this study we investigated the formation and significance of these non-equant fracture patterns to propose a model for their formation. These `abnormal' fracture patterns have not been discussed in the literature and may be important to better understanding the cooling conditions of such lava flows. To test these possibilities we studied Kokostick Butte dacite flow, OR (near South Sister), and Mazama Ridge andesite flow at Mount Rainier, WA. Both of these flows have well developed sheet-like fractures and display evidence of ice-contact during eruption and emplacement. Sheet fractures are long and continuous fractures that have perpendicular connecting fractures forming rectangular columns. The sheet-like fractures are largely parallel to each other on the exposure surface and the connecting fractures vary locally from primary fractures (associated with cooling toward flow interior) to secondary fractures (associated with cooling by water infiltration). Detailed measurements of fracture orientations and spacing were collected at Kokostick Butte and Mazama Ridge to examine the relationship between the sheet fractures and flow geometry. Preliminary results support this relationship and suggest these patterns likely form due to shear associated with small amounts of flow advance by the rapidly cooling lava. Laboratory studies have been undertaken to complement the field observations and measurements. Starch- water experiments have been proven a useful analogue for lava column formation. Various experimental setups involving different mixture thicknesses and compression of the mixture were utilized to simulate the stresses acting during ponding of lava against glacial ice and to produce different fracture morphologies and patterns. Initial results show that compression of the starch slurry results in non-equant fracture patterns with some sheet-like fracturing present.

Mortality in the Vertebroplasty Population

PubMed Central

McDonald, Robert J.; Achenbach, Sara; Atkinson, Elizabeth; Gray, Leigh A.; Cloft, Harry J.; Melton, L. Joseph; Kallmes, David F.

2011-01-01

Purpose Vertebroplasty is an effective treatment for painful compression fractures refractory to conservative management. Since there are limited data regarding the survival characteristics of this patient population, we compared the survival of a treated to an untreated vertebral fracture cohort to determine if vertebroplasty affects mortality rates. Materials and Methods The survival of a treated cohort, comprising 524 vertebroplasty recipients with refractory osteoporotic vertebral compression fractures, was compared to a separate, historical cohort of 589 subjects with fractures not treated by vertebroplasty who were identified from the Rochester Epidemiology Project. Mortality was compared between cohorts using Cox proportional hazard models adjusting for age, gender, and Charlson indices of co-morbidity. Mortality was also correlated with pre-, peri-, and post-procedural clinical metrics (e.g., cement volume utilization, Roland-Morris Disability Questionnaire score, analog pain scales, frequency of narcotic use, and improvements in mobility) within the treated cohort. Results Vertebroplasty recipients demonstrated 77% of the survival expected for individuals of similar age, ethnicity, and gender within the US population. When compared to individuals with both symptomatic and asymptomatic untreated vertebral fractures, vertebroplasty recipients retained a 17% greater mortality risk. However, when compared to symptomatic untreated vertebral fractures, vertebroplasty recipients had no increased mortality following adjustment for differences in age, sex and co-morbidity (HR 1.02; CI 0.82–1.25). In addition, no clinical metrics used to assess the efficacy of vertebroplasty were predictive of survival. Conclusion Vertebroplasty recipients have mortality rates similar to individuals with untreated symptomatic fractures but worse mortality compared to those with asymptomatic vertebral fractures. PMID:21998109

Macro-mesoscopic Fracture and Strength Character of Pre-cracked Granite Under Stress Relaxation Condition

NASA Astrophysics Data System (ADS)

Liu, Junfeng; Yang, Haiqing; Xiao, Yang; Zhou, Xiaoping

2018-05-01

The fracture characters are important index to study the strength and deformation behavior of rock mass in rock engineering. In order to investigate the influencing mechanism of loading conditions on the strength and macro-mesoscopic fracture character of rock material, pre-cracked granite specimens are prepared to conduct a series of uniaxial compression experiments. For parts of the experiments, stress relaxation tests of different durations are also conducted during the uniaxial loading process. Furthermore, the stereomicroscope is adopted to observe the microstructure of the crack surfaces of the specimens. The experimental results indicate that the crack surfaces show several typical fracture characters in accordance with loading conditions. In detail, some cleavage fracture can be observed under conventional uniaxial compression and the fractured surface is relatively rough, whereas as stress relaxation tests are attached, relative slip trace appears between the crack faces and some shear fracture starts to come into being. Besides, the crack faces tend to become smoother and typical terrace structures can be observed in local areas. Combining the macroscopic failure pattern of the specimens, it can be deduced that the duration time for the stress relaxation test contributes to the improvement of the elastic-plastic strain range as well as the axial peak strength for the studied material. Moreover, the derived conclusion is also consistent with the experimental and analytical solution for the pre-peak stage of the rock material. The present work may provide some primary understanding about the strength character and fracture mechanism of hard rock under different engineering environments.

Morphological analysis of astrocytes in the hippocampus in mechanical asphyxiation.

PubMed

Li, Dong-Ri; Ishikawa, Takaki; Quan, Li; Zhao, Dong; Michiue, Tomomi; Zhu, Bao-Li; Wang, Hui Jun; Maeda, Hitoshi

2010-03-01

The present study investigated the morphology of astrocytes in the hippocampus and serum S100B levels in cases of mechanical asphyxia due to neck compression (n=23: atypical hanging, n=7; ligature/manual strangulation, n=16) with regard to the classical autopsy findings, compared with those of other types of asphyxiation (n=9) and acute myocardial infarction/ischemia (AMI, n=20). The decrease in intact astrocyte number, as shown by S100 and GFAP-immunostaining, was larger for asphyxiation due to neck compression compared with that for other asphyxiation and AMI, showing a correlation with the increase in the serum S100B levels. The decrease in intact astrocyte number and increase in serum S100B were closely related to the severity of conjunctival petechial hemorrhage and fracture(s) of the hyoid bone and/or thyroid cartilage in asphyxia due to neck compression. These findings suggest that hippocampal astrocyte injury is caused by cerebral hypoxia accompanied by congestion, especially in mechanical asphyxia due to neck compression. (c) 2009 Elsevier Ireland Ltd. All rights reserved.

Fine characterization rock thermal damage by acoustic emission technique

NASA Astrophysics Data System (ADS)

Kong, Biao; Li, Zenghua; Wang, Enyuan

2018-02-01

This paper examines the differences in the thermal mechanical properties and acoustic emission (AE) characteristics during the deformation and fracture of rock under the action of continuous heating and after high-temperature treatment. Using AE 3D positioning technology, the development and evolution of the internal thermal cracks and the time domain of AE signals in rock were analyzed. High-temperature treatment causes thermal damage to rock. Under the action of continuous heating, the phase characteristics of AE time series correspond to the five stages of rock thermal deformation and fracture, respectively: the micro-defect development stage, the threshold interval of rock micro-cracks, the crack initiation stage, the crack propagation stage, and the crack multistage propagation evolution. When the initial crack propagates, the crack initiation of the rock causes the AE signal to produce a sudden mutation change. Mechanical fraction characteristics during rock uniaxial compression after temperature treatment indicated that the decrease rate of the rock compressive strength, wave velocity, and elastic modulus are relatively large during uniaxial compression tests after high-temperature treatment. During the deformation and fracture of rock under loading, there is faster growth of AE counts and AE events, indicating an increase in the speed of rock deformation and fracture under loading. AE counts show obvious changes during the latter loading stages, whereas AE events show obvious changes during the loading process. The results obtained are valuable for rock thermal stability detection and evaluation in actual underground engineering.

Analysis of Long Bone and Vertebral Failure Patterns.

DTIC Science & Technology

1982-03-01

Roberts, B., 1976. Pathology of degenerative spondylosis in The Lumbar Spine and Back Pain (ed. M. Jayson), New York, Grune & Stratton, Inc., pp. 55-75...compressive loading failed by end plate or vertebral body fracture (Percy, 1957). The fractures were most common in the upper lumbar level, and the fracture...and upper lumbar regions which is supported Iby Perey’s findings (1957). The debris in the hematopoietic spaces appears Ito be bone fragments, but it

Are Geotehrmal Reservoirs Stressed Out?

NASA Astrophysics Data System (ADS)

Davatzes, N. C.; Laboso, R. C.; Layland-Bachmann, C. E.; Feigl, K. L.; Foxall, W.; Tabrez, A. R.; Mellors, R. J.; Templeton, D. C.; Akerley, J.

2017-12-01

Crustal permeability can be strongly influenced by developing connected networks of open fractures. However, the detailed evolution of a fracture network, its extent, and the persistence of fracture porosity are difficult to analyze. Even in fault-hosted geothermal systems, where heat is brought to the surface from depth along a fault, hydrothermal flow is heterogeneously distributed. This is presumably due to variations in fracture density, connectivity, and attitude, as well as variations in fracture permeability caused by sealing of fractures by precipitated cements or compaction. At the Brady Geothermal field in Nevada, we test the relationship between the modeled local stress state perturbed by dislocations representing fault slip or volume changes in the geothermal reservoir inferred from surface deformation measured by InSAR and the location of successful geothermal wells, hydrothermal activity, and seismicity. We postulate that permeability is favored in volumes that experience positive Coulomb stress changes and reduced compression, which together promote high densities of dilatant fractures. Conversely, permeability can be inhibited in locations where Coulomb stress is reduced, compression promotes compaction, or where the faults are poorly oriented in the stress field and consequently slip infrequently. Over geologic time scales spanning the development of the fault system, these local stress states are strongly influenced by the geometry of the fault network relative to the remote stress driving slip. At shorter time scales, changes in fluid pressure within the fracture network constituting the reservoir cause elastic dilations and contractions. We integrate: (1) direct observations of stress state and fractures in boreholes and the mapped geometry of the fault network; (2) evidence of permeability from surface hydrothermal features, production/injection wells and surface deformations related to pumping history; and (3) seismicity to test the correlation between the reservoir geometry and models of the local stress state.

Reverse distal femoral locking compression plate a salvage option in nonunion of proximal femoral fractures.

PubMed

Dumbre Patil, Sampat S; Karkamkar, Sachin S; Patil, Vaishali S Dumbre; Patil, Shailesh S; Ranaware, Abhijeet S

2016-01-01

When primary fixation of proximal femoral fractures with implants fails, revision osteosynthesis may be challenging. Tracts of previous implants and remaining insufficient bone stock in the proximal femur pose unique problems for the treatment. Intramedullary implants like proximal femoral nail (PFN) or surface implants like Dynamic Condylar Screw (DCS) are few of the described implants for revision surgery. There is no evidence in the literature to choose one implant over the other. We used the reverse distal femur locking compression plate (LCP) of the contralateral side in such cases undergoing revision surgery. This implant has multiple options of fixation in proximal femur and its curvature along the length matches the anterior bow of the femur. We aimed to evaluate the efficacy of this implant in salvage situations. Twenty patients of failed primary proximal femoral fractures who underwent revision surgery with reverse distal femoral locking plate from February 2009 to November 2012 were included in this retrospective study. There were 18 subtrochanteric fractures and two ipsilateral femoral neck and shaft fractures, which exhibited delayed union or nonunion. The study included 14 males and six females. The mean patient age was 43.6 years (range 22-65 years) and mean followup period was 52.1 months (range 27-72 months). Delayed union was considered when clinical and radiological signs of union failed to progress at the end of four months from initial surgery. All fractures exhibited union without any complications. Union was assessed clinically and radiologically. One case of ipsilateral femoral neck and shaft fracture required bone grafting at the second stage for delayed union of the femoral shaft fracture. Reverse distal femoral LCP of the contralateral side can be used as a salvage option for failed fixation of proximal femoral fractures exhibiting nonunion.

Fatigue pre-cracking and fracture toughness in polycrystalline tungsten and molybdenum

NASA Astrophysics Data System (ADS)

Taguchi, Katsuya; Nakadate, Kazuhito; Matsuo, Satoru; Tokunaga, Kazutoshi; Kurishita, Hiroaki

2018-01-01

Fatigue pre-cracking performance and fracture toughness in polycrystalline tungsten (W) and molybdenum (Mo) have been investigated in relation to grain boundary (GB) configuration with respect to the crack advance direction. Sub-sized, single edge notched bend (SENB) specimens with three different orientations, R-L (ASTM notation) for a forged Mo rod and L-S and T-S for a rolled W plate, were pre-cracked in two steps: fully uniaxial compression fatigue loading to provoke crack initiation and its stable growth from the notch root, and subsequent 3-point bend (3PB) fatigue loading to extend the crack. The latter step intends to minimize the influence of the residual tensile stresses generated during compression fatigue by moving the crack tip away from the plastic zone. It is shown that fatigue pre-cracking performance, especially pre-crack extension behavior, is significantly affected by the specimen orientation. The R-L orientation, giving the easiest cracking path, permitted crack extension completely beyond the plastic zone, while the L-S and T-S orientations with the thickness cracking direction of the rolled plate sustained the crack lengths around or possibly within the plastic zone size due to difficulty in crack advance through an aligned grain structure. Room temperature fracture toughness tests revealed that the 3PB fatigued specimens exhibited appreciably higher fracture toughness by about 30% for R-L, 40% for L-S and 60% for T-S than the specimens of each orientation pre-cracked by compression fatigue only. This indicates that 3PB fatigue provides the crack tip front out of the residual tensile stress zone by crack extension or leads to reduction in the residual stresses at the crack tip front. Strong dependence of fracture toughness on GB configuration was evident. The obtained fracture toughness values are compared with those in the literature and its strong GB configuration dependence is discussed in connection with the appearance of pop-in.

Micro computed tomography features of laryngeal fractures in a case of fatal manual strangulation.

PubMed

Fais, Paolo; Giraudo, Chiara; Viero, Alessia; Miotto, Diego; Bortolotti, Federica; Tagliaro, Franco; Montisci, Massimo; Cecchetto, Giovanni

2016-01-01

Cases of subtle fatal neck compression are often complicated by the lack of specificity of the post-mortem signs of asphyxia and by the lack of clear signs of neck compression. Herein we present a forensic case of a 45-year-old schizophrenic patient found on the floor of the bedroom of a psychiatric ward in cardiopulmonary arrest and who died after two days in a vegetative state. The deposition of the roommate of the deceased, who claimed responsibility for the killing of the victim by neck compression, was considered unreliable by the prosecutor. Autopsy, toxicological analyses, and multi-slice computed tomography (MSCT), micro computed tomography (micro-CT) and histology of the larynx complex were performed. Particularly, micro-CT analysis of the thyroid cartilage revealed the bilateral presence of ossified triticeous cartilages and the complete fragmentation of the right superior horn of the thyroid, but it additionally demonstrated a fracture on the contralateral superior horns, which was not clearly diagnosable at MSCT. On the basis of the evidence of intracartilaginous laryngeal hemorrhages and bilateral microfracture at the base of the superior horns of the larynx, the death was classified as a case of asphyxia due to manual strangulation. Micro-CT was confirmed as a useful tool in cases of subtle fatal neck compression, for the detection of minute laryngeal cartilage fractures, especially in complex cases with equivocal findings on MSCT. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Simultaneous comparison and assessment of eight remotely sensed maps of Philippine forests

NASA Astrophysics Data System (ADS)

Estoque, Ronald C.; Pontius, Robert G.; Murayama, Yuji; Hou, Hao; Thapa, Rajesh B.; Lasco, Rodel D.; Villar, Merlito A.

2018-05-01

This article compares and assesses eight remotely sensed maps of Philippine forest cover in the year 2010. We examined eight Forest versus Non-Forest maps reclassified from eight land cover products: the Philippine Land Cover, the Climate Change Initiative (CCI) Land Cover, the Landsat Vegetation Continuous Fields (VCF), the MODIS VCF, the MODIS Land Cover Type product (MCD12Q1), the Global Tree Canopy Cover, the ALOS-PALSAR Forest/Non-Forest Map, and the GlobeLand30. The reference data consisted of 9852 randomly distributed sample points interpreted from Google Earth. We created methods to assess the maps and their combinations. Results show that the percentage of the Philippines covered by forest ranges among the maps from a low of 23% for the Philippine Land Cover to a high of 67% for GlobeLand30. Landsat VCF estimates 36% forest cover, which is closest to the 37% estimate based on the reference data. The eight maps plus the reference data agree unanimously on 30% of the sample points, of which 11% are attributable to forest and 19% to non-forest. The overall disagreement between the reference data and Philippine Land Cover is 21%, which is the least among the eight Forest versus Non-Forest maps. About half of the 9852 points have a nested structure such that the forest in a given dataset is a subset of the forest in the datasets that have more forest than the given dataset. The variation among the maps regarding forest quantity and allocation relates to the combined effects of the various definitions of forest and classification errors. Scientists and policy makers must consider these insights when producing future forest cover maps and when establishing benchmarks for forest cover monitoring.

A Changing Number of Alternative States in the Boreal Biome: Reproducibility Risks of Replacing Remote Sensing Products.

PubMed

Xu, Chi; Holmgren, Milena; Van Nes, Egbert H; Hirota, Marina; Chapin, F Stuart; Scheffer, Marten

2015-01-01

Publicly available remote sensing products have boosted science in many ways. The openness of these data sources suggests high reproducibility. However, as we show here, results may be specific to versions of the data products that can become unavailable as new versions are posted. We focus on remotely-sensed tree cover. Recent studies have used this public resource to detect multi-modality in tree cover in the tropical and boreal biomes. Such patterns suggest alternative stable states separated by critical tipping points. This has important implications for the potential response of these ecosystems to global climate change. For the boreal region, four distinct ecosystem states (i.e., treeless, sparse and dense woodland, and boreal forest) were previously identified by using the Collection 3 data of MODIS Vegetation Continuous Fields (VCF). Since then, the MODIS VCF product has been updated to Collection 5; and a Landsat VCF product of global tree cover at a fine spatial resolution of 30 meters has been developed. Here we compare these different remote-sensing products of tree cover to show that identification of alternative stable states in the boreal biome partly depends on the data source used. The updated MODIS data and the newer Landsat data consistently demonstrate three distinct modes around similar tree-cover values. Our analysis suggests that the boreal region has three modes: one sparsely vegetated state (treeless), one distinct 'savanna-like' state and one forest state, which could be alternative stable states. Our analysis illustrates that qualitative outcomes of studies may change fundamentally as new versions of remote sensing products are used. Scientific reproducibility thus requires that old versions remain publicly available.

Biomechanical assessment and 3D finite element analysis of the treatment of tibial fractures using minimally invasive percutaneous plates

PubMed Central

Hu, Xin-Jia; Wang, Hua

2017-01-01

The aim of the present study was to investigate the biomechanical effects of varying the length of a limited contact-dynamic compression plate (LC-DCP) and the number and position of screws on middle tibial fractures, and to provide biomechanical evidence regarding minimally invasive plate osteosynthesis (MIPO). For biomechanical testing, 60 tibias from cadavers (age at mortality, 20–40 years) were used to create middle and diagonal fracture models without defects. Tibias were randomly grouped and analyzed by biomechanic and three-dimensional (3D) finite element analysis. The differences among LC-DCPs of different lengths (6-, 10- and 14-hole) with 6 screws, 14-hole LC-DCPs with different numbers of screws (6, 10 and 14), and 14-hole LC-DCPs with 6 screws at different positions with regard to mechanical characteristics, including compressing, torsion and bending, were examined. The 6-hole LC-DCP had greater vertical compression strain compared with the 10- and 14-hole LC-DCPs (P<0.01), and the 14-hole LC-DCP had greater lateral strain than the 6- and 10-hole LC-DCPs (P<0.01). Furthermore, significant differences in torque were observed among the LC-DPs of different lengths (P<0.01). For 14-hole LC-DCPs with different numbers of screws, no significant differences in vertical strain, lateral strain or torque were detected (P>0.05). However, plates with 14 screws had greater vertical strain compared with those fixed with 6 or 10 screws (P<0.01). For 4-hole LC-DCPs with screws at different positions, vertical compression strain values were lowest for plates with screws at positions 1, 4, 7, 8, 11 and 14 (P<0.01). The lateral strain values and vertical strain values for plates with screws at positions 1, 3, 6, 9, 12 and 14 were significantly lower compared with those at the other positions (P<0.01), and torque values were also low. Thus, the 14-hole LC-DCP was the most stable against vertical compression, torsion and bending, and the 6-hole LC-DCP was the least stable. However, the use of 14 screws with a 14-hole LC-DCP provided less stability against bending than did 6 or 10 screws. Furthermore, fixation with distributed screws, in which some screws were close to the fracture line, provided good stability against compression and torsion, while fixation with screws at the ends of the LC-DCP provided poor stability against bending, compressing and torsion. PMID:28781632

Operative treatment of hip fractures in patients receiving hemodialysis.

PubMed

Tosun, Bilgehan; Atmaca, Halil; Gok, Umit

2010-11-01

Fifteen hips in 13 patients with hip fracture were treated in patients receiving hemodialysis for chronic renal failure. There were four intertrochanteric and 11 femoral neck fractures. 10 of the 11 femoral neck fractures and one of the four intertrochanteric fractures were treated with cemented bipolar hemiarthroplasty. Two intertrochanteric fractures fixed with sliding compression screws. External fixation was used for stabilization in two patients who had femoral neck and intertrochanteric fractures. Two intertrochanteric fractures that were treated with sliding hip screw showed radiological union postoperatively at the 6th month. Of the 11 hemiarthroplasty, four hips developed aseptic loosening (36%). According to Harris hip score grading system, three (37.5%) poor, two (25%) fair, two (25%) good and one (12.5%) case had excellent outcome in the hemiarthroplasty group. The survival of dialysis patients with a hip fracture is markedly reduced. Initial treatment of hemiarthroplasty allows early mobilization and prevents revision surgery.

Undiagnosed vertebral hemangioma causing a lumbar compression fracture and epidural hematoma in a parturient undergoing vaginal delivery under epidural analgesia: a case report.

PubMed

Staikou, Chryssoula; Stamelos, Matthaios; Boutas, Ioannis; Koutoulidis, Vassileios

2015-08-01

Vertebral hemangiomas are benign vascular tumours of the bony spine which are usually asymptomatic. Pregnancy-related anatomical and hormonal changes may lead to expansion of hemangiomas and development of neurological symptoms. We present an unusual case of vertebral fracture due to an undiagnosed hemangioma presenting as postpartum back pain following epidural analgesia. A multiparous female with an unremarkable history developed intense lumbar pain after vaginal delivery under epidural analgesia. The pain was attributed to tissue trauma associated with the epidural technique. The patient had no clinical improvement with analgesics, and her symptoms deteriorated over the following days. A magnetic resonance imaging scan revealed an acute fracture of the second lumbar vertebra (L2) with epidural extension and mild compression of the dural sac, suggesting hemangioma as the underlying cause. The patient underwent successful spinal surgery with pedicle screw fixation to stabilize the fracture. Vertebral fractures secondary to acute expansion of a vertebral hemangioma rarely occur during vaginal delivery. In such cases, the labour epidural technique and analgesia may challenge the physician in making the diagnosis. Postpartum severe back pain should be thoroughly investigated even in the absence of neurological deficits, and osseous spinal pathology should be considered in the differential diagnosis.

Effect of luting cements on the compressive strength of Turkom-Cera all-ceramic copings.

PubMed

Al-Makramani, Bandar M A; Razak, Abdul A A; Abu-Hassan, Mohamed I

2008-02-01

The objective of this study is to investigate the effect of different luting agents on the fracture strength of Turkom-Cera all-ceramic copings. Standardized metal dies were duplicated from a prepared maxillary first premolar tooth using non-precious metal alloy (Wiron 99). Thirty Turkom-Cera copings of 0.6 mm thickness were then fabricated. Three types of luting agents were used: zinc phosphate cement (Elite), glass-ionomer cement (Fuji I), and a dual-cured composite resin cement (Panavia F). Ten copings were cemented with each type. All copings were cemented to their respective dies according to manufacturer's instructions and received a static load of 5 kg for ten minutes. After 24 hours of storage in distilled water at 37 degrees C, the copings were vertically loaded until fracture using an Instron Universal Testing Machine at a crosshead speed of 1 mm/minute. The mode of fracture was then determined. Statistical analysis carried out using analysis of variance (ANOVA) revealed significant differences in the compressive strength between the three groups (P<0.001). The mean fracture strength (in Newtons) of Turkom-Cera copings cemented with Elite, Fuji I, and Panavia F were 1537.4 N, 1294.4 N, and 2183.6 N, respectively. Luting agents have an influence on the fracture resistance of Turkom-Cera copings.

A rare case of multiple pituitary adenomas in an adolescent Cushing disease presenting as a vertebral compression fracture.

PubMed

Song, Ji-Yeon; Mun, Sue-Jean; Sung, Soon-Ki; Hwang, Jae-Yeon; Baik, Seung-Kug; Kim, Jee Yeon; Cheon, Chong-Kun; Kim, Su-Young; Kim, Yoo-Mi

2017-09-01

Cushing disease in children and adolescents, especially with multiple pituitary adenomas (MPAs), is very rare. We report 17-year-old boy with MPAs. He presented with a vertebral compression fracture, weight gain, short stature, headache, and hypertension. On magnetic resonance imaging (MRI), only a left pituitary microadenoma was found. After surgery, transient clinical improvement was observed but headache and hypertension were observed again after 3 months later. Follow-up MRI showed a newly developed right pituitary microadenoma 6 months after the surgery. The need for careful clinical and radiographic follow-up should be emphasized in the search for potential MPAs in patients with persistent Cushing disease.

Adhesion at the interface in cured graphite fiber epoxy-amine resin composites

NASA Technical Reports Server (NTRS)

Needles, Howard L.; Alger, Kenneth W.; Okamoto, Robert

1987-01-01

The effect of high temperature curing on the interface between unsized or epoxy-sized graphite fiber tow and epoxy-amine resin was examined by scanning electron microscopy of compression and freeze fractured specimens. Little or no adhesion was found between the unsized graphite fiber tows and the epoxy-amine resin on curing at 165 C for 17 hrs. Epoxy-sized graphite fibers showed a similar lack of adhesion between the fiber tows and the epoxy-amine resin at 3 and 17 hr cures, although good penetration of the resin into the sized fiber tows had occurred. Interfacial bond strengths for the composites could not be effectively measured by compression fracture of specimens.

Initial versus final fracture of metal-free crowns, analyzed via acoustic emission.

PubMed

Ereifej, Nadia; Silikas, Nick; Watts, David C

2008-09-01

To discriminate between initial and final fracture failure loads of four metal-free crown systems by the conjoint detection of acoustic emission signals during compressive loading. Teeth were prepared and used for crown construction with four crown systems; Vita Mark II (VM II) (Vita Zahnfabrik), IPS e.max Ceram/CAD (CAD) (Ivoclar-Vivadent), IPS e.max Ceram/ZirCAD (ZirCAD) (Ivoclar-Vivadent) and BelleGlass/EverStick (BGES) (Kerr/Stick Tech Ltd.). All samples were loaded in compression via a Co/Cr maxillary first molar tooth at 0.2mm/min and released acoustic signals were collected and analyzed. A minimum number of 15 crowns per group were loaded to final failure and values of loading at initial and final fracture were compared. Additional four samples per group were loaded till fracture initiation and were fractographically examined under the optical microscope. A lower threshold of 50dB was selected to exclude spurious background signals. Initial fracture forces were significantly lower than those of final fracture (p<0.05) in all groups and initial failure AE amplitudes were lower than those of final fracture. Mean initial fracture force of ZirCAD samples (1029.1N) was higher than those of VMII (744.4N), CAD (808.8 N) and BGES (979.7 N). Final fracture of ZirCAD also occurred at significantly higher force values (2091.7 N) than the rest of the groups; VMII (1120.9 N), CAD (1468.9 N) and BGES (1576.6 N). Significantly higher values of initial failure AE amplitude were found in VMII than CAD and BGES while those of final fracture were similar. All crowns observed under the microscope at initial fracture had signs of failure. Whereas the metal-free crowns examined showed significant variations in final failure loads, acoustic emission data showed that they all manifested initial failures at significantly lower load values.

Biomechanics of Sports-Induced Axial-Compression Injuries of the Neck

PubMed Central

Ivancic, Paul C.

2012-01-01

Context Head-first sports-induced impacts cause cervical fractures and dislocations and spinal cord lesions. In previous biomechanical studies, researchers have vertically dropped human cadavers, head-neck specimens, or surrogate models in inverted postures. Objective To develop a cadaveric neck model to simulate horizontally aligned, head-first impacts with a straightened neck and to use the model to investigate biomechanical responses and failure mechanisms. Design Descriptive laboratory study. Setting Biomechanics research laboratory. Patients or Other Participants Five human cadaveric cervical spine specimens. Intervention(s) The model consisted of the neck specimen mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Head-first impacts were simulated at 4.1 m/s into a padded, deformable barrier. Main Outcome Measure(s) Time-history responses were determined for head and neck loads, accelerations, and motions. Average occurrence times of the compression force peaks at the impact barrier, occipital condyles, and neck were compared. Results The first local compression force peaks at the impact barrier (3070.0 ± 168.0 N at 18.8 milliseconds), occipital condyles (2868.1 ± 732.4 N at 19.6 milliseconds), and neck (2884.6 ± 910.7 N at 25.0 milliseconds) occurred earlier than all global compression peaks, which reached 7531.6 N in the neck at 46.6 milliseconds (P < .001). Average peak head motions relative to the torso were 6.0 cm in compression, 2.4 cm in posterior shear, and 6.4° in flexion. Neck compression fractures included occipital condyle, atlas, odontoid, and subaxial comminuted burst and facet fractures. Conclusions Neck injuries due to excessive axial compression occurred within 20 milliseconds of impact and were caused by abrupt deceleration of the head and continued forward torso momentum before simultaneous rebound of the head and torso. Improved understanding of neck injury mechanisms during sports-induced impacts will increase clinical awareness and immediate care and ultimately lead to improved protective equipment, reducing the frequency and severity of neck injuries and their associated societal costs. PMID:23068585

Tension band suture fixation for olecranon fractures.

PubMed

Phadnis, Joideep; Watts, Adam C

2017-10-01

Olecranon fractures are common and often require surgical treatment when displaced. Traditional methods of stabilization using tension band wire fixation and plate fixation achieve adequate union and function but are associated with a high rate of re-operation and wound problems because of prominent metalwork. The purpose of the present article is to describe an all suture technique for fixation of simple olecranon fractures that maintains inter-fragmentary compression, provides bony union and reduces the rate of re-operation caused by prominent metalwork.

Osteopenia and bone fractures in a man with anorexia nervosa and hypogonadism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rigotti, N.A.; Neer, R.M.; Jameson, L.

Women with anorexia nervosa have reduced skeletal mass. Both anorexia and osteopenia are less common in men. We describe a 22-year-old man with anorexia nervosa and severe osteopenia involving both cortical and trabecular bone who developed a pelvic fracture and multiple vertebral compression fractures. He was found to have secondary hypogonadotropic hypogonadism that was reversible with weight gain. This case illustrates the need to consider osteopenia as a potential complication of anorexia nervosa in males as well as females.

Fracture of the fabella.

PubMed

Woo, C C

1988-10-01

A very rare case of traumatic avulsion fracture of the fabella in a middle-age lady, presented as intermittent posterolateral localized knee pain accentuated by compression against the lateral femoral condyle and by active and passive knee extension, is illustrated. The accumulated chronic microtrauma of the osteoarthritic fabello femoral joint in this lady especially during the whip-kick of daily breaststroke swimming for over 30 yr, may precipitate a fabella stress fracture. Radiographs reveal bilateral fabellae with a left bipartite fabella as a stress fracture traversing it without displacement; this later became a completely displaced bipartite avulsion fracture after accidental knee hyperextension. Conservative treatment consisted of anti-inflammatory/analgesic cream, cryotherapy, TENS, strapping and avoiding knee hyperextension.

Tensile and compressive failure modes of laminated composites loaded by fatigue with different mean stress

NASA Technical Reports Server (NTRS)

Rotem, Assa

1990-01-01

Laminated composite materials tend to fail differently under tensile or compressive load. Under tension, the material accumulates cracks and fiber fractures, while under compression, the material delaminates and buckles. Tensile-compressive fatigue may cause either of these failure modes depending on the specific damage occurring in the laminate. This damage depends on the stress ratio of the fatigue loading. Analysis of the fatigue behavior of the composite laminate under tension-tension, compression-compression, and tension-compression had led to the development of a fatigue envelope presentation of the failure behavior. This envelope indicates the specific failure mode for any stress ratio and number of loading cycles. The construction of the fatigue envelope is based on the applied stress-cycles to failure (S-N) curves of both tensile-tensile and compressive-compressive fatigue. Test results are presented to verify the theoretical analysis.

[Minimally invasive cement augmentation of osteoporotic vertebral compression fractures with the new radiofrequency kyphoplasty].

PubMed

Mattyasovszky, S G; Kurth, A A; Drees, P; Gemidji, J; Thomczyk, S; Kafchitsas, K

2014-10-01

Minimally invasive cement augmentation of painful osteoporotic vertebral compression fractures in elderly patients. Painful osteoporotic vertebral compression fractures in elderly patients (> 65 years of age) after conservative therapy failure. Painful aggressive primary tumors of the spine or osteolytic metastases to the spine with high risk of vertebral fracture in the palliative care setting. General contraindications for surgical interventions. Local soft-tissue infection. Osteomyelitis, discitis or systemic infection. Coagulopathy refractory to treatment or bleeding diathesis. Asymptomatic vertebral compression fractures. Burst of the posterior vertebral column with high degree of spinal canal stenosis. Primary or metastatic spinal tumors with epidural growth. Prone position on a radiolucent operating table. Fluoroscopic localization of the fractured vertebra using two conventional C-arm devices (anteroposterior and lateral views). Fluoroscopic localization of the fractured vertebra using two conventional C-arm devices (anteroposterior and lateral views). An introducer is inserted through a small skin incision into the pedicle under fluoroscopic guidance. To create a site- and size-specific three-dimensional cavity in the center of the fractured vertebra, the navigational VertecoR™ MidLine Osteotome was inserted through the correctly sited introducer and guided fluoroscopically. As the MidLine Osteotome allows angulation of the tip up to 90° by rotating the handle, a cavity over the midline of the vertebral body can mainly be created through one pedicle. The radiofrequency activated cohesive ultrahigh viscosity PMMA cement (ER(2) bone cement) is injected stepwise on demand by remote control under continuous pressure from the hydraulic assembly into the vertebral body. Bed rest for 6 h postoperatively in supine position. Early mobilization without a corset on the day of surgery. Specific back and abdominal exercises that strengthen the back and abdominal muscles. Pain dependent increase of weight bearing. Continue osteoporosis therapy and start specific drug therapy according to the local guidlines if necessary. In all, 44 patients (29 women, 15 men) with a mean age of 73.5 years with a total of 62 painful osteoporotic vertebral fractures were treated with RF kyphoplasty from May 2009 until July 2010, and followed over a period of 12 months. The mean operating time per patient was 36.2 min, the operating time per vertebra was 25.7 min. All the patients studied experienced an early and persistent significant pain relief even 12 months after therapy (8 ± 1.4 vs. 2.7 ± 1.9) according to the visual analogue pain scale. According to the Oswestry Disability Index (ODI) as a disease-specific disability measure all the patients improved significantly (p < 0.001) in the level of disability after operative treatment (56.2 ± 18.8 vs. 34.5 ± 16.6). Cement leakage was detected in 17 out of 62 (27.4 %) augmented vertebrae, whereas all the patients with cement leakage remained asymptomatic. One patient had subsequent vertebral fractures after a period of 6 months.

The extrusion test and sensory perception revisited: Some comments on generality and the effect of measurement temperature.

PubMed

Brenner, Tom; Tomczyńska-Mleko, Marta; Mleko, Stanisław; Nishinari, Katsuyoshi

2017-12-01

Relations between sensory perception, extrusion and fracture in shear, extension and compression are examined. Gelatin-based gels are perceived as less firm and less hard than expected based on their mechanical properties compared to polysaccharide gels that have the same mechanical properties at room temperature but melt well above body temperature, underlying the importance of the measurement temperature for gels that melt during mastication. Correlations between parameters from extrusion and compression, extension and shear are verified using mixed polysaccharide gels. We previously reported a high correlation between several sensory attributes and parameters from an extrusion test. The extrusion test showed the most robust correlation, and could be used to assess samples at both extremes of the texture range with respect to elasticity, for example, both samples that could not be extended as their very low elasticity led to their fracture during handling, as well as samples that could not be fractured in compression. Here, we reexamine the validity of the relations reported. We demonstrate the generality of the relations between large deformation tests and extrusion, but the findings underscore the need to take into account the measurement temperature for samples that melt during mastication when correlating instrumental parameters with sensory perception. © 2017 Wiley Periodicals, Inc.

Processing, thermal and mechanical behaviour of PEI/MWCNT/carbon fiber nanostructured laminate

NASA Astrophysics Data System (ADS)

Santos, L. F. P.; Ribeiro, B.; Hein, L. R. O.; Botelho, E. C.; Costa, M. L.

2017-11-01

In this work, nanostructured composites of polyetherimide (PEI) with addition of functionalized multiwall carbon nanotube (MWCNT) were processed via solution mixing. After processing, these nanocomposites were evaluated by thermogravimetry (TGA), dynamic-mechanical analysis (DMA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Subsequently, the nanocomposite was processed with carbon fibers by using hot compression molding. In order to evaluate interlaminar fracture strength, the processed laminates were mechanically evaluated by interlaminar shear strength (ILSS) and compression shear test (CST). Also, the Weibull distribution was employed to help in the statistical treatment of the data obtained from the mechanical tests. With regards to the fracture of the specimens, optical microscopy was used for the evaluation of the material. The addition of 1 wt% of MWCNT in the polymer matrix increased both thermal stability and viscoelastic behavior of the material. These improvements positively impacted the mechanical properties, generating a 16% and 58% increase in the short-beam strength and apparent interlaminar shear, respectively. In addition, it can be verified from morphological analysis of the fracture a change in the failure mode of the laminate by the incorporation of MWCNT. This behavior can be proven from CST test where there was no presence of the shear force by compression.

Fracture mechanisms of glass particles under dynamic compression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parab, Niranjan D.; Guo, Zherui; Hudspeth, Matthew C.

2017-08-01

In this study, dynamic fracture mechanisms of single and contacting spherical glass particles were observed using high speed synchrotron X-ray phase contrast imaging. A modified Kolsky bar setup was used to apply controlled dynamic compressive loading on the soda-lime glass particles. Four different configurations of particle arrangements with one, two, three, and five particles were studied. In single particle experiments, cracking initiated near the contact area between the particle and the platen, subsequently fragmenting the particle in many small sub-particles. In multi-particle experiments, a crack was observed to initiate from the point just outside the contact area between two particles.more » The initiated crack propagated at an angle to the horizontal loading direction, resulting in separation of a fragment. However, this fragment separation did not affect the ability of the particle to withstand further contact loading. On further compression, large number of cracks initiated in the particle with the highest number of particle-particle contacts near one of the particle-particle contacts. The initiated cracks roughly followed the lines joining the contact points. Subsequently, the initiated cracks along with the newly developed sub-cracks bifurcated rapidly as they propagated through the particle and fractured the particle explosively into many small fragments, leaving the other particles nearly intact.« less

Biomechanical characteristics of fixation methods for floating pubic symphysis.

PubMed

Song, Wenhao; Zhou, Dongsheng; He, Yu

2017-03-07

Floating pubic symphysis (FPS) is a relatively rare injury caused by high-energy mechanisms. There are several fixation methods used to treat FPS, including external fixation, subcutaneous fixation, internal fixation, and percutaneous cannulated screw fixation. To choose the appropriate fixation, it is necessary to study the biomechanical performance of these different methods. The goal of this study was to compare the biomechanical characteristics of six methods by finite element analysis. A three-dimensional finite element model of FPS was simulated. Six methods were used in the FPS model, including external fixation (Ext), subcutaneous rod fixation (Sub-rod), subcutaneous plate fixation (Sub-plate), superior pectineal plate fixation (Int-sup), infrapectineal plate fixation (Int-ifa), and cannulated screw fixation (Int-scr). Compressive and rotational loads were then applied in all models. Biomechanical characteristics that were recorded and analyzed included construct stiffness, micromotion of the fracture gaps, von Mises stress, and stress distribution. The construct stiffness of the anterior pelvic ring was decreased dramatically when FPS occurred. Compressive stiffness was restored by the three internal fixation and Sub-rod methods. Unfortunately, rotational stiffness was not restored satisfactorily by the six methods. For micromotion of the fracture gaps, the displacement was reduced significantly by the Int-sup and Int-ifa methods under compression. The internal fixation methods and Sub-plate method performed well under rotation. The maximum von Mises stress of the implants was not large. For the plate-screw system, the maximum von Mises stress occurred over the region of the fracture and plate-screw joints. The maximum von Mises stress appeared on the rod-screw and screw-bone interfaces for the rod-screw system. The present study showed the biomechanical advantages of internal fixation methods for FPS from a finite element view. Superior stabilization of the anterior pelvic ring and fracture gaps was obtained by internal fixation. Subcutaneous fixation had satisfactory outcomes as well. Sub-rod fixation offered good anti-compression, while the Sub-plate fixation provided favorable anti-rotational capacity.

Adjacent vertebral body fracture following vertebroplasty with polymethylmethacrylate or calcium phosphate cement: biomechanical evaluation of the cadaveric spine.

PubMed

Nouda, Shinya; Tomita, Seiji; Kin, Akihiro; Kawahara, Kunihiko; Kinoshita, Mitsuo

2009-11-15

A biomechanical study using human cadaveric thoracolumbar spinal columns. To compare the effect of treatment by vertebroplasty (VP) with polymethylmethacrylate cement and VP with calcium phosphate cement on the creation of adjacent vertebral body fracture following VP. Adjacent vertebral body fractures have been reported as a complication following VP. Twenty-four spinal columns (T10-L2) from human cadavers were subjected to dual energy radiograph absorptiometry to assess bone mineral density. They were divided into the P group and C group, and experimental vertebral compression fractures were created at T12 vertebrae. T12 vertebrae were augmented with polymethylmethacrylate and calcium phosphate cement in the P group and C group, respectively. Each spinal column was compressed until a new fracture occurred at any vertebra, and the location of newly fractured vertebra and failure load was investigated. There was no significant difference in bone mineral density at each level within each group. In the P group, a new fracture occurred at T10 in 2 specimens, T11 in 8, and L1 in 2. In the C group, it occurred at T10 in 1 specimen, T11 in 2, L1 in 1, and T12 (treated vertebra) in 8. The failure loads of the spinal column were 1774.8+/-672.3 N and 1501.2+/-556.5 N in the P group and C group, respectively. There was no significant difference in the failure load of the spinal column between each group. New vertebral fractures occurred at the vertebra adjacent to augmented vertebrae in the P group and in the augmented vertebrae in the C group. The difference in the fractured site may be because of the difference in strength between the 2 bone filler materials. Therefore, the strength of bone filler materials is considered a risk factor in developing adjacent vertebral body fractures after VP.

Kyphoplasty vs conservative treatment: a case-control study in 110 post-menopausal women population. Is kyphoplasty better than conservative treatment?

PubMed

Colangelo, D; Nasto, L A; Genitiempo, M; Formica, V M; Autore, G; Pambianco, V; Tamburrelli, F C; Cerulli, G; Pola, E

2015-11-01

Osteoporosis is a highly prevalent disease worldwide. Consequences of vertebral osteoporotic fractures include pain and progressive vertebral collapse resulting in spinal kyphosis, decreased quality of life, disability and mortality. Minimally invasive procedures represent an advance to the treatment of osteoporotic VCFs. Despite encouraging results reported by many authors, surgical intervention in an osteoporotic spine is fraught with difficulties. Advanced patients age and comorbidities are of great concern. We designed a retrospective case-control study on 110 post-menopausal women consecutively visited at our institution. Study population was split in a surgical and a conservative cohort, according to the provided treatment. Kyphoplasty treated patients had lower back pain VAS scores at 1 month as compared with conservatively treated patients (p < 0.05). EQ5D validated questionnaire also showed a better quality of life at 1 month for surgically treated patients (p < 0.05). SF-12 scores showed greater improvements at 1 month and 3 months with statistically significant difference between the two groups just at 3 months (p < 0.05). At 12 months, scores from all scales were not statistically different between the two cohorts, although surgically treated patients showed better trends than conservatively treated patients in pain and quality of life. Kyphoplasty was able to restore more than 54.55% of the original segmental kyphosis, whereas patients in conservative cohort lost 6.67% of the original segmental kyphosis on average. Kyphoplasty is a modern minimal invasive surgery, allowing faster recovery than bracing treatment. It can avoid the deformity in kyphosis due to VCF. In fact, the risk to develop a new vertebral fracture after the first one is very high.

Dual small fragment plating improves screw-to-screw load sharing for mid-diaphyseal humeral fracture fixation: a finite element study.

PubMed

Kosmopoulos, Victor; Luedke, Colten; Nana, Arvind D

2015-01-01

A smaller humerus in some patients makes the use of a large fragment fixation plate difficult. Dual small fragment plate constructs have been suggested as an alternative. This study compares the biomechanical performance of three single and one dual plate construct for mid-diaphyseal humeral fracture fixation. Five humeral shaft finite element models (1 intact and 4 fixation) were loaded in torsion, compression, posterior-anterior (PA) bending, and lateral-medial (LM) bending. A comminuted fracture was simulated by a 1-cm gap. Fracture fixation was modelled by: (A) 4.5-mm 9-hole large fragment plate (wide), (B) 4.5-mm 9-hole large fragment plate (narrow), (C) 3.5-mm 9-hole small fragment plate, and (D) one 3.5-mm 9-hole small fragment plate and one 3.5-mm 7-hole small fragment plate. Model A showed the best outcomes in torsion and PA bending, whereas Model D outperformed the others in compression and LM bending. Stress concentrations were located near and around the unused screw holes for each of the single plate models and at the neck of the screws just below the plates for all the models studied. Other than in PA bending, Model D showed the best overall screw-to-screw load sharing characteristics. The results support using a dual small fragment locking plate construct as an alternative in cases where crutch weight-bearing (compression) tolerance may be important and where anatomy limits the size of the humerus bone segment available for large fragment plate fixation.

Comparison of the compressive strength of 3 different implant design systems.

PubMed

Pedroza, Jose E; Torrealba, Ysidora; Elias, Augusto; Psoter, Walter

2007-01-01

The aims of this study were twofold: to compare the static compressive strength at the implant-abutment interface of 3 design systems and to describe the implant abutment connection failure mode. A stainless steel holding device was designed to align the implants at 30 degrees with respect to the y-axis. Sixty-nine specimens were used, 23 for each system. A computer-controlled universal testing machine (MTS 810) applied static compression loading by a unidirectional vertical piston until failure. Specimens were evaluated macroscopically for longitudinal displacement, abutment looseness, and screw and implant fracture. Data were analyzed by analysis of variance (ANOVA). The mean compressive strength for the Unipost system was 392.5 psi (SD +/-40.9), for the Spline system 342.8 psi (SD+/-25.8), and for the Screw-Vent system 269.1 psi (SD+/-30.7). The Unipost implant-abutment connection demonstrated a statistically significant superior mechanical stability (P < or = .009) compared with the Spline implant system. The Spline implant system showed a statistically significant higher compressive strength than the Screw-Vent implant system (P < or =.009). Regarding failure mode, the Unipost system consistently broke at the same site, while the other systems failed at different points of the connection. The Unipost system demonstrated excellent fracture resistance to compressive forces; this resistance may be attributed primarily to the diameter of the abutment screw and the 2.5 mm counter bore, representing the same and a unique piece of the implant. The Unipost implant system demonstrated a statistically significant superior compressive strength value compared with the Spline and Screw-Vent systems, at a 30 degrees angulation.

High speed X-ray phase contrast imaging of energetic composites under dynamic compression

NASA Astrophysics Data System (ADS)

Parab, Niranjan D.; Roberts, Zane A.; Harr, Michael H.; Mares, Jesus O.; Casey, Alex D.; Gunduz, I. Emre; Hudspeth, Matthew; Claus, Benjamin; Sun, Tao; Fezzaa, Kamel; Son, Steven F.; Chen, Weinong W.

2016-09-01

Fracture of crystals and frictional heating are associated with the formation of "hot spots" (localized heating) in energetic composites such as polymer bonded explosives (PBXs). Traditional high speed optical imaging methods cannot be used to study the dynamic sub-surface deformation and the fracture behavior of such materials due to their opaque nature. In this study, high speed synchrotron X-ray experiments are conducted to visualize the in situ deformation and the fracture mechanisms in PBXs composed of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals and hydroxyl-terminated polybutadiene binder doped with iron (III) oxide. A modified Kolsky bar apparatus was used to apply controlled dynamic compression on the PBX specimens, and a high speed synchrotron X-ray phase contrast imaging (PCI) setup was used to record the in situ deformation and failure in the specimens. The experiments show that synchrotron X-ray PCI provides a sufficient contrast between the HMX crystals and the doped binder, even at ultrafast recording rates. Under dynamic compression, most of the cracking in the crystals was observed to be due to the tensile stress generated by the diametral compression applied from the contacts between the crystals. Tensile stress driven cracking was also observed for some of the crystals due to the transverse deformation of the binder and superior bonding between the crystal and the binder. The obtained results are vital to develop improved understanding and to validate the macroscopic and mesoscopic numerical models for energetic composites so that eventually hot spot formation can be predicted.

High speed X-ray phase contrast imaging of energetic composites under dynamic compression

DOE PAGES

Parab, Niranjan D.; Roberts, Zane A.; Harr, Michael H.; ...

2016-09-26

Fracture of crystals and subsequent frictional heating are associated with formation of hot spots in energetic composites such as polymer bonded explosives (PBXs). Traditional high speed optical imaging methods cannot be used to study the dynamic sub-surface deformation and fracture behavior of such materials due to their opaque nature. In this study, high speed synchrotron X-ray experiments are conducted to visualize the in situ deformation and fracture mechanisms in PBXs manufactured using octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals and hydroxyl-terminated polybutadiene (HTPB) binder. A modified Kolsky bar apparatus was used to apply controlled dynamic compression on the PBX specimens, and a high speedmore » synchrotron X-ray phase contrast imaging (PCI) setup was used to record the in situ deformation and failure in the specimens. The experiments show that synchrotron X-ray PCI provides a sufficient contrast between the HMX crystals and the doped binder, even at ultrafast recording rates. Under dynamic compression, most of the cracking in the crystals was observed to be due to the tensile stress generated by the diametral compression applied from the contacts between the crystals. Tensile stress driven cracking was also observed for some of the crystals due to the transverse deformation of the binder and superior bonding between the crystal and the binder. In conclusion, the obtained results are vital to develop improved understanding and to validate the macroscopic and mesoscopic numerical models for energetic composites so that eventually hot spot formation can be predicted.« less

The shear fracture toughness, KIIc, of graphite

DOE PAGES

Burchell, Timothy D.; Erdman, III, Donald L.

2015-11-05

In this study, the critical shear stress intensity factor, KIIc, here-in referred to as the shear fracture toughness, KIIc (MPa m), of two grades of graphite are reported. The range of specimen volumes was selected to elucidate any specimen size effect, but smaller volume specimen tests were largely unsuccessful, shear failure did not occur between the notches as expected. This was probably due to the specimen geometry causing the shear fracture stress to exceed the compressive failure stress. In subsequent testing the specimen geometry was altered to reduce the compressive footprint and the notches (slits) made deeper to reduce themore » specimen's ligament length. Additionally, we added the collection of Acoustic Emission (AE) during testing to assist with the identification of the shear fracture load. The means of KIIc from large specimens for PCEA and NBG-18 are 2.26 MPa m with an SD of 0.37 MPa m and 2.20 MPa m with an SD of 0.53 MPa m, respectively. The value of KIIc for both graphite grades was similar, although the scatter was large. In this work we found the ratio of KIIc/ KIc ≈ 1.6. .« less

Biomechanical comparison of 3.0 mm headless compression screw and 3.5 mm cortical bone screw in a canine humeral condylar fracture model.

PubMed

Gonsalves, Mishka N; Jankovits, Daniel A; Huber, Michael L; Strom, Adam M; Garcia, Tanya C; Stover, Susan M

2016-09-20

To compare the biomechanical properties of simulated humeral condylar fractures reduced with one of two screw fixation methods: 3.0 mm headless compression screw (HCS) or 3.5 mm cortical bone screw (CBS) placed in lag fashion. Bilateral humeri were collected from nine canine cadavers. Standardized osteotomies were stabilized with 3.0 mm HCS in one limb and 3.5 mm CBS in the contralateral limb. Condylar fragments were loaded to walk, trot, and failure loads while measuring construct properties and condylar fragment motion. The 3.5 mm CBS-stabilized constructs were 36% stiffer than 3.0 mm HCS-stabilized constructs, but differences were not apparent in quality of fracture reduction nor in yield loads, which exceeded expected physiological loads during rehabilitation. Small residual fragment displacements were not different between CBS and HCS screws. Small fragment rotation was not significantly different between screws, but was weakly correlated with moment arm length (R² = 0.25). A CBS screw placed in lag fashion provides stiffer fixation than an HCS screw, although both screws provide similar anatomical reduction and yield strength to condylar fracture fixation in adult canine humeri.

Compressive fracture resistance of the marginal ridge in large Class II tunnels restored with cermet and composite resin.

PubMed

Ehrnford, L E; Fransson, H

1994-01-01

Compressive fracture resistance of the marginal ridge was studied in large tunnel preparations, before and after restoration with cermet (Ketac Silver, ESPE), a universal hybrid composite (Superlux, DMG) and an experimental composite. Each group was represented by six tunnels in extracted upper premolars. The tunnels were prepared by the use of round burs up to size #6. Remaining ridge width was 1.5 mm and ridge height 1.7 mm in the contact area. The ridge was loaded to fracture by a rod placed perpendicular to the ridge. Generally this resulted in a shear fracture of the restoration. There was no significant reinforcement of the ridge by the cermet whereas the composites both reinforced by the same magnitude, averaging 62%. It was concluded that the ridge could be considered a "megafiller" where contact need to be preserved and contour protected against proximal and occlusal wear of the restoration. Clinically there would therefore be good reasons to save even ridge areas with very low inherent strength. Based on the present study composite resin might therefore be the filling material of choice for such tunnel preparations.

Treatment of spinal fractures with paraplegia.

PubMed

Riska, E B; Myllynen, P

1981-01-01

Of 206 patients with vertebral fractures in the thoraco-lumbar spine with spinal cord injuries, an antero-lateral decompression with stabilization of the injured segment of the vertebral column was undertaken in 56 cases. In all these cases there was a compression of the spinal cord from the front. 8 patients made a complete recovery, 31 a good recovery, and 6 were improved. In 8 patients no improvement was noted. 2 patients developed pressure sores later and 1 patient died one year after the operation of uraemia. 22 patients out of 55 got a normal function of the bladder and 25 patients out of 54 a normal function of the anal sphincter. 16 patients out of 17 made a complete or good recovery after removal of a displaced rotated vertebral bony fragment from the spinal canal, and 7 patients out of 9 with wedge shaped fractures. In our clinic today, in cases of vertebral fractures with neural involvement, reduction and internal fixation with Harrington rods and fusion of the injured segment is undertaken as soon as possible, also during the night. If narrowing of the neural canal and compression of the spinal cord are verified, a decompression operation with interbody fusion is undertaken during the next days.

Paleostress Reconstruction from 3D seismic, Natural Fracture and Calcite Twin Analyses: Structural Insights into the Otway Basin, Australia

NASA Astrophysics Data System (ADS)

Burgin, Hugo; Amrouch, Khalid; Holford, Simon

2017-04-01

The Otway Basin, Australia, is of particular interest due to its significance as an Australian hydrocarbon producing province and a major global CO2 burial project. Structural data was collected in the form of natural fractures from wellbore image logs and outcrop in addition to calcite twin analyses, within formations from the mid cretaceous from both on and offshore. Evidence for four structural events within the study area have been identified including NE-SW and NW-SE orientated extension, in addition to a NW-SE compressive event. Natural fracture data also reveals a previously "un-detected" NE-SW compression within the Otway Basin. This study presents the first investigation of paleostress environments within the region from micro, meso and macro scale tectonic data in both onshore and offshore in addition to the first quantification of differential paleostresses. This work highlights the importance of a comprehensive understanding of four dimensional stress evolution within the sedimentary basins of Australia's southern margin.

Investigation on thermal oxidative aging of nitrile rubber (NBR) O-rings under compression stress

NASA Astrophysics Data System (ADS)

Liu, X. R.; Zhang, W. F.; Lou, W. T.; Huang, Y. X.; Dai, W.

2017-11-01

The degradation behaviors of nitrile rubber O-rings exposure to air under compression were investigated at three elevated temperatures. The physical and mechanical properties of the aging samples before and after exposure at selected time were studied by measuring weight loss, tensile strength and elongation at break. The Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and fracture morphology were used to reveal the microstructural changes of the aging samples. The results indicate that the weight decreased with exposure time and temperature. Based on the results of the crosslinking density, the crosslinking predominates during the most of aging process. The significant changes in tensile strength and elongation at break also indicate the severe degradation in air. The fracture morphology results show that the fracture surface after 64 days of exposure to air turns rough and present defects. The ATR-FTIR results demonstrate that the hydroxyl groups were formed for the samples aged in air.

Strength and fracture energy of foamed concrete incorporating rice husk ash and polypropylene mega-mesh 55

NASA Astrophysics Data System (ADS)

Jaini, Z. M.; Rum, R. H. M.; Boon, K. H.

2017-10-01

This paper presents the utilization of rice husk ash (RHA) as sand replacement and polypropylene mega-mesh 55 (PMM) as fiber reinforcement in foamed concrete. High pozzolanic reaction and the ability to become filler make RHA as a strategic material to enhance the strength and durability of foamed concrete. Furthermore, the presence of PMM optimizes the toughness of foamed concrete in resisting shrinkage and cracking. In this experimental study, cube and cylinder specimens were prepared for the compression and splitting-tensile tests. Meanwhile, notched beam specimens were cast for the three-point bending test. It was found that 40% RHA and 9kg/m3 PMM contribute to the highest strength and fracture energy. The compressive, tensile and flexural strengths are 32MPa, 2.88MPa and 6.68MPa respectively, while the fracture energy achieves 42.19N/m. The results indicate high potential of RHA and PMM in enhancing the mechanical properties of foamed concrete.

[Vascular and neurological complications of supracondylar humeral fractures in children].

PubMed

Masár, J

2007-10-01

The author reports two cases of pediatric patients with supracondylar humeral fractures complicated by concomitant vascular injury. One of the patients also presented with neurological symptoms from compression of the ulnar and median nerves. In the case of vascular injury only, it was necessary to resect a 1-cm segment of the brachial artery which was thrombosed due to intimal disruption. In the other case, surgery was not indicated immediately; however, liberation of the nervus ulnaris and nervus medianus was later required because of nerve compression by the scar and bone. The author considers the exact diagnosis, precise reduction and stable fixation of a fracture to be most important for a good outcome of treatment. Any associated vascular injury is indicated for surgery only after a thorough diagnostic consideration, and may not be needed in every case. The most decisive factor is the clinical presentation. Injury to the nerve system is indicated for surgical treatment at a later period, at 3 months post-injury at the earliest.

Dynamic fracture behavior of single and contacting Poly(methyl methacrylate) particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parab, Niranjan D.; Guo, Zherui; Hudspeth, Matthew C.

Fracture behaviors of single, two, and multiple contacting spherical Poly (methyl methacrylate) (PMMA) particles were recorded using high speed synchrotron X-ray phase contrast imaging. A miniaturized Kolsky bar setup was used to apply dynamic compressive loading on the PMMA particles. In both single and two particle experiments, cracking initiated near the center of the particles and propagated towards the contacts. The crack bifurcated near the contact points for single particle experiments, thus forming conical fragments. The crack bifurcation and subsequent conical fragment formation was observed only at the particle-particle contact for two particle experiments. The particles were observed to fracturemore » in hemispherical fragments normal to the contact plane in the multiparticle experiments. The observed failure mechanisms strongly suggest that the maximum tensile stress near the center of the particle is the critical parameter governing fracture of the particles. Moreover, the compressive stress under the contact areas led to the bifurcation and subsequent conical fragment formation.« less

Osteoporosis of the slender smoker. Vertebral compression fractures and loss of metacarpal cortex in relation to postmenopausal cigarette smoking and lack of obesity.

PubMed

Daniell, H W

1976-03-01

A group of thirty-eight women under age 70 who sustained vertebral compression fractures during minor trauma included more postmenopausal smokers than a group of 34 similar women with fractures resulting from major trauma and more than a group of 572 other women. Advanced idiopathic osteoporosis occurring before age 65 was found rarely among nonsmokers. The percent cortical area at the second metacarpal midpoint was measured in 103 white women aged 40 to 49 years, and 208 white women aged 60 to 69 years. In the younger group, no quantitative differences were demonstrated between bones of the obese and the nonobese or between smokers and nonsmokers. In contrast, among the older group, postmenopausal smokers exhibited much more bone loss than did nonsmokers (P less than .001), and nonobese women demonstrated much more bone loss than did obese women, this difference being most striking among smokers.

Dynamic fracture behavior of single and contacting Poly(methyl methacrylate) particles

DOE PAGES

Parab, Niranjan D.; Guo, Zherui; Hudspeth, Matthew C.; ...

2017-09-19

Fracture behaviors of single, two, and multiple contacting spherical Poly (methyl methacrylate) (PMMA) particles were recorded using high speed synchrotron X-ray phase contrast imaging. A miniaturized Kolsky bar setup was used to apply dynamic compressive loading on the PMMA particles. In both single and two particle experiments, cracking initiated near the center of the particles and propagated towards the contacts. The crack bifurcated near the contact points for single particle experiments, thus forming conical fragments. The crack bifurcation and subsequent conical fragment formation was observed only at the particle-particle contact for two particle experiments. The particles were observed to fracturemore » in hemispherical fragments normal to the contact plane in the multiparticle experiments. The observed failure mechanisms strongly suggest that the maximum tensile stress near the center of the particle is the critical parameter governing fracture of the particles. Moreover, the compressive stress under the contact areas led to the bifurcation and subsequent conical fragment formation.« less

Evaluation of superplastic forming and co-diffusion bonding of Ti-6Al-4V titanium alloy expanded sandwich structures

NASA Technical Reports Server (NTRS)

Arvin, G. H.; Israeli, L.; Stolpestad, J. H.; Stacher, G. W.

1981-01-01

The application of the superplastic forming/diffusion bonding (SPF/DB) process to supersonic cruise research is investigated. The capability of an SPF/DB titanium structure to meet the structural requirements of the inner wing area of the NASA arrow-wing advanced supersonic transport design is evaluated. Selection of structural concepts and their optimization for minimum weight, SPF/DB process optimization, fabrication of representative specimens, and specimen testing and evaluation are described. The structural area used includes both upper and lower wing panels, where the upper wing panel is used for static compression strength evaluation and the lower panel, in tension, is used for fracture mechanics evaluations. The individual test specimens, cut from six large panels, consist of 39 static specimens, 10 fracture mechanics specimens, and one each full size panel for compression stability and fracture mechanics testing. Tests are performed at temperatures of -54 C (-65 F), room temperature, and 260 C (500 F).

Thermoplastic composites for veneering posterior teeth-a feasibility study.

PubMed

Gegauff, Anthony G; Garcia, Jose L; Koelling, Kurt W; Seghi, Robert R

2002-09-01

This pilot study was conducted to explore selected commercially-available thermoplastic composites that potentially had physical properties superior to currently available dental systems for restoring esthetic posterior crowns. Polyurethane, polycarbonate, and poly(ethylene/tetrafluoroethylene) (ETFE) composites and unfilled polyurethane specimens were injection molded to produce shapes adaptive to five standardized mechanical tests. The mechanical testing included abrasive wear rate, yield strength, apparent fracture toughness (strength ratio), flexural strength, and compressive strength. Compared to commercially available dental composites, abrasion wear rates were lower for all materials tested, yield strength was greater for the filled polycarbonates and filled polyurethane resins, fracture toughness testing was invalid (strength ratios were calculated for comparison of the pilot test materials), flexural strength was roughly similar except for the filled ETFE which was significantly greater, and compressive strength was lower. Commercially available thermoplastic resin composites, such as polyurethane, demonstrate the potential for development of an artificial crown material which exceeds the mechanical properties of currently available esthetic systems, if compressive strength can be improved.

COMPRESSIVE FATIGUE IN TITANIUM DENTAL IMPLANTS SUBMITTED TO FLUORIDE IONS ACTION

PubMed Central

Ribeiro, Ana Lúcia Roselino; Noriega, Jorge Roberto; Dametto, Fábio Roberto; Vaz, Luís Geraldo

2007-01-01

The aim of this study was to assess the influence of a fluoridated medium on the mechanical properties of an internal hexagon implant-abutment set, by means of compression, mechanical cycling and metallographic characterization by scanning electronic microscopy. Five years of regular use of oral hygiene with a sodium fluoride solution content of 1500 ppm were simulated, immersing the samples in this medium for 184 hours, with the solutions being changed every 12 hours. Data were analyzed at a 95% confidence level with Fisher's exact test. After the action of fluoride ions, a negative influence occurred in the mechanical cycling test performed in a servohydraulic machine (Material Test System-810) set to a frequency of 15 Hz with 100,000 cycles and programmed to 60% of the maximum resistance of static compression test. The sets tended to fracture by compression on the screw, characterized by mixed ruptures with predominance of fragile fracture, as observed by microscopy. An evidence of corrosion by pitting on sample surfaces was found after the fluoride ions action. It may be concluded that prolonged contact with fluoride ions is harmful to the mechanical properties of commercially pure titanium structures. PMID:19089148

Modification of elastic stable intramedullary nailing with a 3rd nail in a femoral spiral fracture model - results of biomechanical testing and a prospective clinical study.

PubMed

Kaiser, Martin M; Stratmann, Christine; Zachert, Gregor; Schulze-Hessing, Maaike; Gros, Nina; Eggert, Rebecca; Rapp, Marion

2014-01-08

Elastic stable intramedullary nailing (ESIN) is the standard treatment for displaced diaphyseal femoral fractures in children. However, high complication rates (10-50%) are reported in complex fractures. This biomechanical study compares the stiffness with a 3rd nail implanted to that in the classical 2C-shaped configuration and presents the application into clinical practice. For each of the 3 configurations of ESIN-osteosynthesis with titanium nails eight composite femoral grafts (Sawbones®) with an identical spiral fracture were used: 2C configuration (2C-shaped nails, 2 × 3.5 mm), 3CM configuration (3rd nail from medial) and 3CL configuration (3rd nail from lateral). Each group underwent biomechanical testing in 4-point bending, internal/external rotation and axial compression. 2C and 3CM configurations showed no significant differences in this spiroid type fracture model. 3CL had a significantly higher stiffness during anterior-posterior bending, internal rotation and 9° compression than 2C, and was stiffer in the lateral-medial direction than 3CM. The 3CL was less stable during p-a bending and external rotation than both the others. As biomechanical testing showed a higher stability for the 3CL configuration in two (a-p corresponding to recurvation and 9° compression to shortening) of three directions associated with the most important clinical problems, we added a 3rd nail in ESIN-osteosynthesis for femoral fractures. 11 boys and 6 girls (2.5-15 years) were treated with modified ESIN of whom 12 were '3CL'; due to the individual character of the fractures 4 patients were treated with '3CM' (third nail from medial) and as an exception 1 adolescent with 4 nails and one boy with plate osteosynthesis. No additional stabilizations or re-operations were necessary. All patients achieved full points in the Harris-Score at follow-up; no limb length discrepancy occurred. The 3CL configuration provided a significantly higher stiffness than 2C and 3CM configurations in this biomechanical model. These results were successfully transmitted into clinical practice. All children, treated by 3CL or 3CM according to the individual character of each fracture, needed no additional stabilization and had no Re-Do operations. As a consequence, at our hospital all children with femoral diaphyseal fractures with open physis are treated with this modified ESIN-technique.

Late extensor pollicis longus rupture following plate fixation in Galeazzi fracture dislocation

PubMed Central

Sabat, Dhananjaya; Dabas, Vineet; Dhal, Anil

2014-01-01

Late rupture of extensor pollicis longus (EPL) tendon after Galeazzi fracture dislocation fixation is an unknown entity though it is a well-established complication following distal radius fractures. We report the case of a 55-year old male who presented with late EPL tendon rupture 4 months following internal fixation of Galeazzi fracture dislocation with a Locking Compression Plate (LCP). He was managed with extensor indicis proprius (EIP) transfer to restore thumb extension. At 4 years followup, functional result of the transfer was good. We identify possible pitfalls with this particular patient and discuss how to avoid them in future. PMID:25143650

Conjugate fracture pairs in the Molina Member of the Wasatch Formation, Piceance basin, Colorado: Implications for fracture origins and hydrocarbon production/exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenz, J.C.

1997-05-01

The sandstones of the Molina Member of the Wasatch Formation in the Piceance basin of northwestern Colorado contain a suite of fractures that have a conjugate-pair geometry. The fractures are vertical and intersect at an acute angle of between 20 and 40 degrees. Although direct evidence of shear is rare, the fracture surfaces commonly display small steps. The fracture geometries suggest that the maximum compressive stress during fracturing was in the plane of the acute angle of the conjugate fractures: the steps are interpreted as broken-face manifestations of very low angle en echelon fractures, formed within exceptionally narrow zones ofmore » incipient shear. In contrast to the highly anisotropic permeability enhancement created by subparallel vertical extension fractures in the underlying Mesaverde Formation, the conjugate pairs in the Molina sandstones should create a well connected and relatively isotropic mesh of fracture conductivity. Increases in stress magnitudes and anisotropy during production drawdown of reservoir pressures should cause shear offsets along the fractures, initially enhancing permeability.« less

Fracture behaviors under pure shear loading in bulk metallic glasses

NASA Astrophysics Data System (ADS)

Chen, Cen; Gao, Meng; Wang, Chao; Wang, Wei-Hua; Wang, Tzu-Chiang

2016-12-01

Pure shear fracture test, as a special mechanical means, had been carried out extensively to obtain the critical information for traditional metallic crystalline materials and rocks, such as the intrinsic deformation behavior and fracture mechanism. However, for bulk metallic glasses (BMGs), the pure shear fracture behaviors have not been investigated systematically due to the lack of a suitable test method. Here, we specially introduce a unique antisymmetrical four-point bend shear test method to realize a uniform pure shear stress field and study the pure shear fracture behaviors of two kinds of BMGs, Zr-based and La-based BMGs. All kinds of fracture behaviors, the pure shear fracture strength, fracture angle and fracture surface morphology, are systematically analyzed and compared with those of the conventional compressive and tensile fracture. Our results indicate that both the Zr-based and La-based BMGs follow the same fracture mechanism under pure shear loading, which is significantly different from the situation of some previous research results. Our results might offer new enlightenment on the intrinsic deformation and fracture mechanism of BMGs and other amorphous materials.

Fracture behaviors under pure shear loading in bulk metallic glasses.

PubMed

Chen, Cen; Gao, Meng; Wang, Chao; Wang, Wei-Hua; Wang, Tzu-Chiang

2016-12-23

Pure shear fracture test, as a special mechanical means, had been carried out extensively to obtain the critical information for traditional metallic crystalline materials and rocks, such as the intrinsic deformation behavior and fracture mechanism. However, for bulk metallic glasses (BMGs), the pure shear fracture behaviors have not been investigated systematically due to the lack of a suitable test method. Here, we specially introduce a unique antisymmetrical four-point bend shear test method to realize a uniform pure shear stress field and study the pure shear fracture behaviors of two kinds of BMGs, Zr-based and La-based BMGs. All kinds of fracture behaviors, the pure shear fracture strength, fracture angle and fracture surface morphology, are systematically analyzed and compared with those of the conventional compressive and tensile fracture. Our results indicate that both the Zr-based and La-based BMGs follow the same fracture mechanism under pure shear loading, which is significantly different from the situation of some previous research results. Our results might offer new enlightenment on the intrinsic deformation and fracture mechanism of BMGs and other amorphous materials.

A Simplified Way for the Stabilization of Pediatric Mandibular Fracture With an Occlusal Splint.

PubMed

Demirkol, Mehmet; Demirkol, Nermin; Abdo, Omar Hasan; Aras, Mutan Hamdi

2016-06-01

The management of pediatric mandibular fractures is challenging for maxillofacial surgeons due to ongoing mandibular growth involving tooth buds. The treatment of such fractures has been a topic of much research. Generally accepted methods for the treatment of mandibular parasymphyseal or symphyseal fractures in children are conservative approaches involving the use of acrylic splints, lateral compression with an open-cap splint stabilized by circummandibular wiring, and maxillomandibular fixation with an arch bar and eyelet wiring. The aim of this technical note was to describe a straightforward approach to the treatment of pediatric mandibular fractures, in which an occlusal splint is secured to prevent trauma to the soft tissue, without the need for general anesthesia.

The Metacarpal Locked Intramedullary Nail: Comparative Biomechanical Evaluation of New Implant Design for Metacarpal Fractures.

PubMed

Boonyasirikool, Chinnakart; Tanakeatsakul, Sakkarin; Niempoog, Sunyarn

2015-04-01

The optimal fixation of metacarpal fracture should provide sufficient stability to permit early functionfor all types of fracture. However; it must preserve surrounding soft tissue during application and not require secondary removal due to its prominence. The prototype of metacarpal locked intramedullary nail (MCLN) was designed by our institute aiming to achieve those allfeatures. To biomechanically test our newly designed, locked metacarpal nail and compare with common current available fixation methods. Thirty chicken humeri were devided into 3 groups (n = 1 per group) according tofixation techniques: MCLN, 1.5 mm miniplate (Synthes), and Kirschner wire. After complete fixation, all specimens were osteotomized at mid-shaft creating transverse fractures. Five specimens from each group were tested by load of failure under axial compression, and another five under bending force. In axial compression model, the loads tofailure in MCLN group was greatest (460 ± 17 N), which was significant higher than the Kirschner wire group. The MCLN group also showed the highest load to failure in bending test (341 ± 10 N). This value reaches statistical significance when compared with plate and Kirschner wire groups. The MCLN construct provided higher stability than miniplate and Kirschner wire fixation both in axial and bending mode. Together with the minimally invasive and soft tissue-friendly design concept, this study suggests that MCLN is promising fixation option for metacarpal fracture.

Fracture patterns in the Zagros fold-and-thrust belt, Kurdistan Region of Iraq

NASA Astrophysics Data System (ADS)

Reif, Daniel; Decker, Kurt; Grasemann, Bernhard; Peresson, Herwig

2012-11-01

Fracture data have been collected in the Kurdistan Region of Iraq, which is a poorly accessible and unexplored area of the Zagros. Pre to early folding NE-SW striking extensional fractures and NW-SE striking contractive elements represent the older set affecting the exposed multilayer of the area. These latter structures are early syn-folding and followed by folding-related mesostructural assemblages, which include elements striking parallel to the axial trend of major folds (longitudinal fractures). Bedding perpendicular joints and veins, and extensional faults belonging to this second fracture set are located in the outer arc of exposed anticlines, whilst longitudinal reverse faults locate in the inner arcs. Consistently, these elements are associated with syn-folding tangential longitudinal strain. The younger two sets are related to E-W extension and NNE-SSW to N-S shortening, frequently displaying reactivation of the older sets. The last shortening event, which is described along the entire Zagros Belt, probably relates with the onset of N-S compression induced by the northward movement of the Arabian plate relative to the Eurasian Plate. In comparison between the inferred palaeostrain directions and the kinematics of recent GPS measurements, we conclude that the N-S compression and the partitioning into NW-SE trending folds and NW to N trending strike-slip faults likely remained unchanged throughout the Neogene tectonic history of the investigated area.

Arthroscopic-assisted Locking Compression Plate clavicular hook fixation for unstable fractures of the lateral end of the clavicle: a prospective study

PubMed Central

Lee, Kwang Won; Kim, Kap Jung; Kim, Yong In; Kwon, Won Cho; Choy, Won Sik

2009-01-01

The aim of this prospective study was to assess the clinical outcomes of an unstable fracture of the lateral end of the clavicle treated with an arthroscopic-assisted locking compressive plate (LCP) clavicular hook plate. Twenty-three patients underwent arthroscopic assisted LCP clavicular hook plate fixation for these fractures. All patients achieved clinical and radiological union over a mean of 4.2 months (range, 3.4–5 months). Four patients (17%) showed some degree of acromial osteolysis. Three patients (13%) showed radiological signs of arthrosis of the acromioclavicular joint. In one patient, a second fracture (stress) was observed between the medial two screws of the plate without an additional injury. Five patients (22%) showed subacromial bursitis on dynamic ultrasonography. The mean Constant and Murley score was 91 points (range, 81–98). The average level of pain in the shoulder at rest and on abduction was 1 (range, 0–2) and 2.4 (range, 0–4), respectively. Based on our experience, arthroscopic-assisted LCP hook plate fixation for the treatment of unstable fractures of the lateral end of the clavicle is not without complications. However, it is an acceptable alternative method that is easy to apply with good results. Furthermore, it prevents rotator cuff impingement, allows early mobilisation and maintains the acromioclavicular joint biomechanics. PMID:19998033

Fracture toughness of SiC/Al metal matrix composite

NASA Technical Reports Server (NTRS)

Flom, Yury; Parker, B. H.; Chu, H. P.

1989-01-01

An experimental study was conducted to evaluate fracture toughness of SiC/Al metal matrix composite (MMC). The material was a 12.7 mm thick extrusion of 6061-T6 aluminum alloy with 40 v/o SiC particulates. Specimen configuration and test procedure conformed to ASTM E399 Standard for compact specimens. It was found that special procedures were necessary to obtain fatigue cracks of controlled lengths in the preparation of precracked specimens for the MMC material. Fatigue loading with both minimum and maximum loads in compression was used to start the precrack. The initial precracking would stop by self-arrest. Afterwards, the precrack could be safely extended to the desired length by additional cyclic tensile loading. Test results met practically all the E399 criteria for the calculation of plane strain fracture toughness of the material. A valid K sub IC value of the SiC/Al composite was established as K sub IC = 8.9 MPa square root of m. The threshold stress intensity under which crack would cease to grow in the material was estimated as delta K sub th = 2MPa square root of m for R = 0.09 using the fatigue precracking data. Fractographic examinations show that failure occurred by the micromechanism involved with plastic deformation although the specimens broke by brittle fracture. The effect of precracking by cyclic loading in compression on fracture toughness is included in the discussion.

Isolated displaced non-union of a triquetral body fracture: a case report.

PubMed

Rasoli, Sonia; Ricks, Matthew; Packer, Greg

2012-02-10

Fractures of the body of the triquetral bone are the second most common carpal fractures, and these fractures can be missed on plain X-ray. Although non-union of triquetral body fractures is very rare, such cases are associated with considerable morbidity and reduction in functional activity. We report the case of a 29-year-old Caucasian British man who sustained an isolated displaced triquetral body fracture that resulted in non-union, who was treated surgically. We describe an original operative management for this debilitating injury. An open reduction and internal fixation using double headed compression screws was performed, without bone grafting, and with early immobilization of the wrist. We propose this novel approach and advocate early clinical suspicion of triquetral body fractures in patients with a history of fall on an outstretched hand and ulnar sided wrist pain. We recommend evaluation using computed tomography or magnetic resonance imaging scanning.

Fracture resistance and primary failure mode of endodontically treated teeth restored with a carbon fiber-reinforced resin post system in vitro.

PubMed

Raygot, C G; Chai, J; Jameson, D L

2001-01-01

This study was undertaken to characterize the fracture resistance and mode of fracture of endodontically treated incisors restored with cast post-and-core, prefabricated stainless steel post, or carbon fiber-reinforced composite post systems. Ten endodontically treated teeth restored with each technique were subjected to a compressive load delivered at a 130-degree angle to the long axis until the first sign of failure was noted. The fracture load and the mode of fracture were recorded. The failure loads registered in the three groups were not significantly different. Between 70%, and 80% of teeth from any of the three groups displayed fractures that were located above the simulated bone level. The use of carbon fiber-reinforced composite posts did not change the fracture resistance or the failure mode of endodontically treated central incisors compared to the use of metallic posts.

[Forensic Analysis of the Characteristics of Pelvic Fracture in 65 Road Traffic Accident Death Cases].

PubMed

Zhang, W

2016-12-01

To analyze the characteristics and mechanisms of pelvic fractures in the cases of road traffic accident deaths. Total 65 cases of road traffic accident deaths with pelvic fracture were collected, and the sites, characteristics and injury mechanisms of pelvic fracture were statistically analyzed. Among the 65 cases of pelvic fracture, 38 cases of dislocation of sacroiliac joint were found, and most combined with pubis symphysis separation or fracture of pubis. In the fractures of pubis, ischium and acetabulum, linear fractures were most common, while comminuted fractures were most common in sacrum and coccyx fractures. There were 54 cases combined with pelvic soft tissue injury, and 8 cases with pelvic organ injury and 44 cases with abdominal organ injury. In the types of pelvic ring injury, 32 cases were separation, 49.32%, followed by compression, 26.15% and only one case was verticality, 1.54%. Detailed and comprehensive examination of the body and determination of the pelvic fracture type contribute to analyze the mechanisms of injury. Copyright© by the Editorial Department of Journal of Forensic Medicine

Cushing disease

MedlinePlus

... Fatigue Frequent infections Headache Increased thirst and urination High blood pressure Diabetes ... Cushing disease include: Compression fractures in the spine Diabetes High blood pressure Infections Kidney stones Mood or other psychiatric problems

Fracture mechanics analyses of ceramic/veneer interface under mixed-mode loading.

PubMed

Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui

2014-11-01

Few studies have focused on the interface fracture performance of zirconia/veneer bilayered structure, which plays an important role in dental all-ceramic restorations. The purpose of this study was to evaluate the fracture mechanics performance of zirconia/veneer interface in a wide range of mode-mixities (at phase angles ranging from 0° to 90°), and to examine the effect of mechanical properties of the materials and the interface on the fracture initiation and crack path of an interfacial crack. A modified sandwich test configuration with an oblique interfacial crack was proposed and calibrated to choose the appropriate geometry dimensions by means of finite element analysis. The specimens with different interface inclination angles were tested to failure under three-point bending configuration. Interface fracture parameters were obtained with finite element analyses. Based on the interfacial fracture mechanics, three fracture criteria for crack kinking were used to predict crack initiation and propagation. In addition, the effects of residual stresses due to coefficient of thermal expansion mismatch between zirconia and veneer on the crack behavior were evaluated. The crack initiation and propagation were well predicted by the three fracture criteria. For specimens at phase angle of 0, the cracks propagated in the interface; whereas for all the other specimens the cracks kinked into the veneer. Compressive residual stresses in the veneer can improve the toughness of the interface structure. The results suggest that, in zirconia/veneer bilayered structure the veneer is weaker than the interface, which can be used to explain the clinical phenomenon that veneer chipping rate is larger than interface delamination rate. Consequently, a veneer material with larger fracture toughness is needed to decrease the failure rate of all-ceramic restorations. And the coefficient of thermal expansion mismatch of the substrates can be larger to produce larger compressive stresses in the veneer. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Biomechanical Analysis of 2 Constructs for Metacarpal Spiral Fracture Fixation in a Cadaver Model: 2 Large Screws Versus 3 Small Screws.

PubMed

Eu-Jin Cheah, Andre; Behn, Anthony W; Comer, Garet; Yao, Jeffrey

2017-12-01

Surgeons confronted with a long spiral metacarpal fracture may choose to fix it solely with lagged screws. A biomechanical analysis of a metacarpal spiral fracture model was performed to determine whether 3 1.5-mm screws or 2 2.0-mm screws provided more stability during bending and torsional loading. Second and third metacarpals were harvested from 12 matched pairs of fresh-frozen cadaveric hands and spiral fractures were created. One specimen from each matched pair was fixed with 2 2.0-mm lagged screws whereas the other was fixed with 3 1.5-mm lagged screws. Nine pairs underwent combined cyclic cantilever bending and axial compressive loading followed by loading to failure. Nine additional pairs were subjected to cyclic external rotation while under a constant axial compressive load and were subsequently externally rotated to failure under a constant axial compressive load. Paired t tests were used to compare cyclic creep, stiffness, displacement, rotation, and peak load levels. Average failure torque for all specimens was 7.2 ± 1.7 Nm. In cyclic torsional testing, the group with 2 screws exhibited significantly less rotational creep than the one with 3 screws. A single specimen in the group with 2 screws failed before cyclic bending tests were completed. No other significant differences were found between test groups during torsional or bending tests. Both constructs were biomechanically similar except that the construct with 2 screws displayed significantly less loosening during torsional cyclic loading, although the difference was small and may not be clinically meaningful. Because we found no obvious biomechanical advantage to using 3 1.5-mm lagged screws to fix long spiral metacarpal fractures, the time efficiency and decreased implant costs of using 2-2.0 mm lagged screws may be preferred. Copyright © 2017 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Biomechanical principles and mechanobiologic aspects of flexible and locked plating.

PubMed

Claes, Lutz

2011-02-01

The goal of minimally invasive surgery in extramedullary internal fixation has led to the development of flexible plates, bridging plates, and locked internal fixators. The change from conventional compression plates to these new implants, however, resulted in different biomechanics of fixation and different mechanobiologic processes for fracture healing. The aim of a flexible fixation is the stimulation of fracture healing by callus formation. Fracture healing follows mechanobiologic rules based mainly on interfragmentary strain, which is dependent on the stability of the fixation construct and the type of fracture. Knowledge of the mechanobiologic processes and the factors influencing the stability of fracture fixation are necessary for the surgeon to choose the correct technique for fracture fixation. Problems in the selection of the correct technique and limitations with the available implants as well as possible future developments are discussed.

Comminuted distal femur closed fractures: a new application of the Ilizarov concept of compression-distraction.

PubMed

El-Tantawy, Ahmad; Atef, Ashraf

2015-04-01

The treatment of intra-articular distal femur fractures with severe metaphyseal comminution is challenging. It is important to choose a technique that provides secure fixation, minimum tissue handling, and early ambulation. The aim of this work was to evaluate the outcomes of application of Ilizarov concept as an early definitive treatment of comminuted distal femur closed fractures. A total of 17 male patients (mean age 28.53±6.33 years) presented with comminuted distal femur fractures (with 10 type C2 and 7 type C3-2 fractures according to AO/ASIF system) were included in this prospective study. Initial fixation of the articular fragments was done by inter-fragmentary screws, percutaneously through a limited open approach, and stabilization was completed by Ilizarov fixator. The procedure included acute shortening, through the comminution, followed by gradual re-distraction to compensate the created shortening. Radiological and functional results were assessed according to ASAMI evaluation system. The mean amount of intra-operative shortening was 3.68±0.53 cm. The mean external fixation index was 37.24±2.53 days/cm. The mean follow-up period was 18.18±1.91 months. All fractures united primarily in an average 137.65±4.12 days, with no evident angular deformity or limb-length discrepancy. None of the cases required a second major procedure or bone graft. The functional results were excellent in three cases, good in 12, and fair in two patients. The Ilizarov concept of acute compression-distraction is a valuable alternative for the treatment of distal femur fractures with severe metaphyseal comminution.

Biomechanical Assessment of the Dorsal Spanning Bridge Plate in Distal Radius Fracture Fixation: Implications for Immediate Weight-Bearing.

PubMed

Huang, Jerry I; Peterson, Bret; Bellevue, Kate; Lee, Nicolas; Smith, Sean; Herfat, Safa

2017-04-01

The goal of this study was to compare the biomechanical stability of a 2.4-mm dorsal spanning bridge plate with a volar locking plate (VLP) in a distal radius fracture model, during simulated crutch weight-bearing. Five paired cadaveric forearms were tested. A 1-cm dorsal wedge osteotomy was created to simulate an unstable distal radius fracture with dorsal comminution. Fractures were fixed with a VLP or a dorsal bridge plate (DBP). Specimens were mounted to a crutch handle, and optical motion-tracking sensors were attached to the proximal and distal segments. Specimens were loaded in compression at 1 mm/s on a servohydraulic test frame until failure, defined as 2 mm of gap site displacement. The VLP construct was significantly more stable to axial load in a crutch weight-bearing model compared with the DBP plate (VLP: 493 N vs DBP: 332 N). Stiffness was higher in the VLP constructs, but this was not statistically significant (VLP: 51.4 N/mm vs DBP: 32.4 N/mm). With the crutch weight-bearing model, DBP failed consistently with wrist flexion and plate bending, whereas VLP failed with axial compression at the fracture site and dorsal collapse. Dorsal spanning bridge plating is effective as an internal spanning fixator in treating highly comminuted intra-articular distal radius fracture and prevents axial collapse at the radiocarpal joint. However, bridge plating may not offer advantages in early weight-bearing or transfer in polytrauma patients, with less axial stability in our crutch weight-bearing model compared with volar plating. A stiffer 3.5-mm DBP or use of a DBP construct without the central holes may be considered for distal radius fractures if the goal is early crutch weight-bearing through the injured extremity.

Outcome of Repair of Distal Radial and Ulnar Fractures in Dogs Weighing 4 kg or Less Using a 1.5-mm Locking Adaption Plate or 2.0-mm Limited Contact Dynamic Compression Plate.

PubMed

Nelson, Thomas A; Strom, Adam

2017-11-01

Objectives  Retrospective evaluation of repairing distal radial and ulnar fractures in small breed dogs with the Synthes 1.5-mm locking Adaption plate system and compare results in a similar group of patients repaired with the Synthes 2.0-mm limited contact-dynamic compression plate (LC-DCP). Methods  Electronic medical records from one specialty referral centre were reviewed from March 21, 2010, to October 9, 2015, for patients weighing less than or equal to 4 kg that had a distal one-third radial and ulnar fracture repaired with a Synthes 1.5-mm locking adaption plate or Synthes 2.0-mm LC-DCP. Further inclusion criteria included application of the plate to the cranial surface of the radius via open reduction and internal fixation. Results  Six 1.5-mm Adaption plates and 7 2.0-mm LC-DCPs were used to repair 13 distal radial and ulnar fractures in 12 dogs. There were three major complications in the 1.5-mm adaption plate group (one plate fracture, one screw pull-out and one fracture through a distal screw hole) and one major complication in the 2.0-mm LC-DCP group due to a re-fracture. All patients without a complication had good or excellent functional outcome. Clinical Significance  The authors recommend that the 1.5-mm Adaption plate be used only when a 2.0-mm LC-DCP would not allow for a minimum of two screws in the distal segment and at the discretion of the surgeon. Schattauer GmbH Stuttgart.

Fracture in Compression of Brittle Solids

DTIC Science & Technology

1983-08-01

SUPPLEMENTARY NOTES 19. KEY WORDS (Continue on reverse aide It necesaray and id:5ntily by block number) Acoustic Emission High Strength Steel Compression...mechanistic models are related to the phenomenological developments in dilatational plasticity that have been applied widely in concrete technology. The...is reviewed in some detail, both from the point of view of fundamentals as well as technological applications. Experimental verification of models is

Two-Dimensional Imaging Velocimetry of Heterogeneous Flow and Brittle Failure in Diamond

NASA Astrophysics Data System (ADS)

Ali, S. J.; Smith, R.; Erskine, D.; Eggert, J.; Celliers, P. M.; Collins, G. W.; Jeanloz, R.

2014-12-01

Understanding the nature and dynamics of heterogeneous flow in diamond subjected to shock compression is important for many fields of research, from inertial confinement fusion to the study of carbon rich planets. Waves propagating through a shocked material can be significantly altered by the various deformation mechanisms present in shocked materials, including anisotropic sound speeds, phase transformations, plastic/inelastic flow and brittle failure. Quantifying the spatial and temporal effects of these deformation mechanisms has been limited by a lack of diagnostics capable of obtaining simultaneous micron resolution spatial measurements and nanosecond resolution time measurements. We have utilized the 2D Janus High Resolution Velocimeter at LLNL to study the time and space dependence of fracture in shock-compressed diamond above the Hugoniot elastic limit. Previous work on the OMEGA laser facility (Rochester) has shown that the free-surface reflectivity of μm-grained diamond samples drops linearly with increasing sample pressure, whereas under the same conditions the reflectivity of nm-grained samples remains unaffected. These disparate observations can be understood by way of better documenting fracture in high-strain compression of diamond. To this end, we have imaged the development and evolution of elastic-wave propagation, plastic-wave propagation and fracture networks in the three primary orientations of single-crystal diamond, as well as in microcrystalline and nanocrystalline diamond, and find that the deformation behavior depends sensitively on the orientation and crystallinity of the diamonds.

Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions.

PubMed

Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

2015-01-01

Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source locations manifest such that AE events are highly correlated with a strength recovery coefficient; the AE events show a decreasing tendency when the coefficient is larger than 1, and vice versa. This study provides a feasible scheme for the reinforcement of fractured rock masses in underground constructions and reveals an internal mechanism of the crushing process for restored rock masses, which has certain instructive significance.

Strength Restoration of Cracked Sandstone and Coal under a Uniaxial Compression Test and Correlated Damage Source Location Based on Acoustic Emissions

PubMed Central

Feng, Xiaowei; Zhang, Nong; Zheng, Xigui; Pan, Dongjiang

2015-01-01

Underground rock masses have shown a general trend of natural balance over billions of years of ground movement. Nonetheless, man-made underground constructions disturb this balance and cause rock stability failure. Fractured rock masses are frequently encountered in underground constructions, and this study aims to restore the strength of rock masses that have experienced considerable fracturing under uniaxial compression. Coal and sandstone from a deep-buried coal mine were chosen as experimental subjects; they were crushed by uniaxial compression and then carefully restored by a chemical adhesive called MEYCO 364 with an innovative self-made device. Finally, the restored specimens were crushed once again by uniaxial compression. Axial stress, axial strain, circumferential strain, and volumetric strain data for the entire process were fully captured and are discussed here. An acoustic emission (AE) testing system was adopted to cooperate with the uniaxial compression system to provide better definitions for crack closure thresholds, crack initiation thresholds, crack damage thresholds, and three-dimensional damage source locations in intact and restored specimens. Several remarkable findings were obtained. The restoration effects of coal are considerably better than those of sandstone because the strength recovery coefficient of the former is 1.20, whereas that of the latter is 0.33, which indicates that MEYCO 364 is particularly valid for fractured rocks whose initial intact peak stress is less than that of MEYCO 364. Secondary cracked traces of restored sandstone almost follow the cracked traces of the initial intact sandstone, and the final failure is mainly caused by decoupling between the adhesive and the rock mass. However, cracked traces of restored coal only partially follow the traces of intact coal, with the final failure of the restored coal being caused by both bonding interface decoupling and self-breakage in coal. Three-dimensional damage source locations manifest such that AE events are highly correlated with a strength recovery coefficient; the AE events show a decreasing tendency when the coefficient is larger than 1, and vice versa. This study provides a feasible scheme for the reinforcement of fractured rock masses in underground constructions and reveals an internal mechanism of the crushing process for restored rock masses, which has certain instructive significance. PMID:26714324

Development and characterization of genipin cross-linked gelatin based composites incorporated with vegetable-tanned collagen fiber (vcf)

USDA-ARS?s Scientific Manuscript database

Collagen fibers obtained from solid fibrous wastes generated in tannery have a high potential of being used in developing green composites. Earlier studies in our laboratory demonstrate that nonwoven composites can be derived from collagen fiber network using paper-making technology. The purpose of ...

Development and characterization of genipin cross-linked gelatin based composites incorporated with vegetable-tanned collagen fiber (VCF)

USDA-ARS?s Scientific Manuscript database

Collagen fibers obtained from solid fibrous wastes generated in tannery have a high potential of being used in developing green composites. Earlier studies in our laboratory demonstrated that nonwoven composites can be derived from collagen fiber network using paper-making technology. The purpose of...

Jannovar: a java library for exome annotation.

PubMed

Jäger, Marten; Wang, Kai; Bauer, Sebastian; Smedley, Damian; Krawitz, Peter; Robinson, Peter N

2014-05-01

Transcript-based annotation and pedigree analysis are two basic steps in the computational analysis of whole-exome sequencing experiments in genetic diagnostics and disease-gene discovery projects. Here, we present Jannovar, a stand-alone Java application as well as a Java library designed to be used in larger software frameworks for exome and genome analysis. Jannovar uses an interval tree to identify all transcripts affected by a given variant, and provides Human Genome Variation Society-compliant annotations both for variants affecting coding sequences and splice junctions as well as untranslated regions and noncoding RNA transcripts. Jannovar can also perform family-based pedigree analysis with Variant Call Format (VCF) files with data from members of a family segregating a Mendelian disorder. Using a desktop computer, Jannovar requires a few seconds to annotate a typical VCF file with exome data. Jannovar is freely available under the BSD2 license. Source code as well as the Java application and library file can be downloaded from http://compbio.charite.de (with tutorial) and https://github.com/charite/jannovar. © 2014 WILEY PERIODICALS, INC.

Mapping national scale land cover disturbance for the continental United States, 2006 to 2010

NASA Astrophysics Data System (ADS)

Hansen, M. C.; Potapov, P. V.; Egorov, A.; Roy, D. P.; Loveland, T. R.

2011-12-01

Data from the Web-Enabled Landsat Data (WELD) project were used to quantify forest cover loss and bare ground gain dynamics for the continental United States at a 30 meter spatial resolution from 2006 to 2010. Results illustrate the land cover dynamics associated with forestry, urbanization and other medium to long-term cover conversion processes. Ephemeral changes, such as crop rotations and fallows or inundation, were not quantified. Forest disturbance is pervasive at the national-scale, while increasing bare ground is found in growing urban areas as well as in mining regions. The methods applied are an outgrowth of the Vegetation Continuous Field (VCF) method, initially employed with MODIS data and then WELD data to map percent cover variables. As in our previous work with MODIS in mapping forest change, we applied the VCF method to characterize forest cover loss and bare ground gain probability per pixel. Additional themes will be added to provide a more comprehensive picture of national-scale land dynamics based on these initial results using WELD.

Surgical repair of femoral fractures in New World camelids: five cases (1996-2003).

PubMed

Shoemaker, R W; Wilson, D G

2007-04-01

Five New World camelids were admitted to the Western College of Veterinary Medicine between 1996 and 2003 for evaluation of femoral fractures. There were three alpacas and two llamas. Four of the animals were female and three were less than 3 months of age. Fracture configurations consisted of distal physeal fractures (three), a comminuted diaphyseal/metaphyseal fracture, and a transverse diaphyseal fracture. Fractures were diagnosed with a combination of physical examination and radiographs in all cases. All five fractures were repaired with internal fixation and three animals were discharged from the hospital with fractures that healed. One cria underwent successful internal fixation but died from pulmonary oedema during recovery from anaesthesia. Postoperative complications were rare and limited to inadequate fracture stability in one alpaca and prolonged recovery to weight bearing in another. One llama with a comminuted metaphyseal fracture, repaired with a 4.5 mm dynamic compression plate, subsequently had catastrophic failure of the bone 17 days after surgery. Overall the clients were pleased with the outcome of discharged animals. Although femoral fractures are considered rare, they pose a unique opportunity for the large animal veterinarian to successfully achieve fracture union with the aid of internal fixation.

Augmentation of failed human vertebrae with critical un-contained lytic defect restores their structural competence under functional loading: An experimental study.

PubMed

Alkalay, Ron N; von Stechow, Dietrich; Hackney, David B

2015-07-01

Lytic spinal lesions reduce vertebral strength and may result in their fracture. Vertebral augmentation is employed clinically to provide mechanical stability and pain relief for vertebrae with lytic lesions. However, little is known about its efficacy in strengthening fractured vertebrae containing lytic metastasis. Eighteen unembalmed human lumbar vertebrae, having simulated uncontained lytic defects and tested to failure in a prior study, were augmented using a transpedicular approach and re-tested to failure using a wedge fracture model. Axial and moment based strength and stiffness parameters were used to quantify the effect of augmentation on the structural response of the failed vertebrae. Effects of cement volume, bone mineral density and vertebral geometry on the change in structural response were investigated. Augmentation increased the failed lytic vertebral strength [compression: 85% (P<0.001), flexion: 80% (P<0.001), anterior-posterior shear: 95%, P<0.001)] and stiffness [(40% (P<0.05), 53% (P<0.05), 45% (P<0.05)]. Cement volume correlated with the compressive strength (r(2)=0.47, P<0.05) and anterior-posterior shear strength (r(2)=0.52, P<0.05) and stiffness (r(2)=0.45, P<0.05). Neither the geometry of the failed vertebrae nor its pre-fracture bone mineral density correlated with the volume of cement. Vertebral augmentation is effective in bolstering the failed lytic vertebrae compressive and axial structural competence, showing strength estimates up to 50-90% of historical values of osteoporotic vertebrae without lytic defects. This modest increase suggests that lytic vertebrae undergo a high degree of structural damage at failure, with strength only partially restored by vertebral augmentation. The positive effect of cement volume is self-limiting due to extravasation. Copyright © 2015. Published by Elsevier Ltd.

A Nonlocal Peridynamic Plasticity Model for the Dynamic Flow and Fracture of Concrete.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vogler, Tracy; Lammi, Christopher James

A nonlocal, ordinary peridynamic constitutive model is formulated to numerically simulate the pressure-dependent flow and fracture of heterogeneous, quasi-brittle ma- terials, such as concrete. Classical mechanics and traditional computational modeling methods do not accurately model the distributed fracture observed within this family of materials. The peridynamic horizon, or range of influence, provides a characteristic length to the continuum and limits localization of fracture. Scaling laws are derived to relate the parameters of peridynamic constitutive model to the parameters of the classical Drucker-Prager plasticity model. Thermodynamic analysis of associated and non-associated plastic flow is performed. An implicit integration algorithm is formu-more » lated to calculate the accumulated plastic bond extension and force state. The gov- erning equations are linearized and the simulation of the quasi-static compression of a cylinder is compared to the classical theory. A dissipation-based peridynamic bond failure criteria is implemented to model fracture and the splitting of a concrete cylinder is numerically simulated. Finally, calculation of the impact and spallation of a con- crete structure is performed to assess the suitability of the material and failure models for simulating concrete during dynamic loadings. The peridynamic model is found to accurately simulate the inelastic deformation and fracture behavior of concrete during compression, splitting, and dynamically induced spall. The work expands the types of materials that can be modeled using peridynamics. A multi-scale methodology for simulating concrete to be used in conjunction with the plasticity model is presented. The work was funded by LDRD 158806.« less

Analysis of Vertebral Bone Strength, Fracture Pattern, and Fracture Location: A Validation Study Using a Computed Tomography-Based Nonlinear Finite Element Analysis

PubMed Central

Imai, Kazuhiro

2015-01-01

Finite element analysis (FEA) is an advanced computer technique of structural stress analysis developed in engineering mechanics. Because the compressive behavior of vertebral bone shows nonlinear behavior, a nonlinear FEA should be utilized to analyze the clinical vertebral fracture. In this article, a computed tomography-based nonlinear FEA (CT/FEA) to analyze the vertebral bone strength, fracture pattern, and fracture location is introduced. The accuracy of the CT/FEA was validated by performing experimental mechanical testing with human cadaveric specimens. Vertebral bone strength and the minimum principal strain at the vertebral surface were accurately analyzed using the CT/FEA. The experimental fracture pattern and fracture location were also accurately simulated. Optimization of the element size was performed by assessing the accuracy of the CT/FEA, and the optimum element size was assumed to be 2 mm. It is expected that the CT/FEA will be valuable in analyzing vertebral fracture risk and assessing therapeutic effects on osteoporosis. PMID:26029476

Do mesoscale faults near the tip of an active strike-slip fault indicate regional or local stress?

NASA Astrophysics Data System (ADS)

Yamaji, Atsushi

2017-04-01

Fault-slip analysis is used in Japan after the Great Tohoku Earthquake (2011) to judge the stability of fractures in the foundations of nuclear power plants. In case a fault-slip datum from a fracture surface is explained by the present stress condition, the fracture is thought to have a risk to be activated as a fault. So, it is important to understand the relative significance of regional and local stresses. To answer the question whether mesoscale faults indicate regional or local stress, fault-slip data were collected from the walls of a trenching site of the Nojima Fault in central Japan—an active, dextral, strike-slip fault. The fault gave rise to the 1995 Kobe earthquake, which killed more than 6000 people. The trench was placed near the fault tip, which produced compressional and extensional local stress conditions on the sides of the fault near the tip. A segment of the fault, which ruptured the surface in 1995, bounded Cretaceous granite and latest Pliocene sediments in the trench. As a result, the stress inversion of the data from the mesoscale faults observed in the trench showed both the local stresses. The present WNW-ESE regional compression was found from the compressive side, but was not in the extensional side, probably because local extension surpassed the regional compression. Instead, the regional N-S compression of the Early Pleistocene was found from the extensional side. From this project, we got the lesson that fault-slip analysis reveals regional and local stresses, and that local stress sometimes masks regional one. This work was supported by a science project of "Drilling into Fault Damage Zone" (awarded to A. Lin) of the Secretariat of Nuclear Regulation Authority (Japan).

Fracture Gap Reduction With Variable-Pitch Headless Screws.

PubMed

Roebke, Austin J; Roebke, Logan J; Goyal, Kanu S

2018-04-01

Fully threaded, variable-pitch, headless screws are used in many settings in surgery and have been extensively studied in this context, especially in regard to scaphoid fractures. However, it is not well understood how screw parameters such as diameter, length, and pitch variation, as well as technique parameters such as depth of drilling, affect gap closure. Acutrak 2 fully threaded variable-pitch headless screws of various diameters (Standard, Mini, and Micro) and lengths (16-28 mm) were inserted into polyurethane blocks of "normal" and "osteoporotic" bone model densities using a custom jig. Three drilling techniques (drill only through first block, 4 mm into second block, or completely through both blocks) were used. During screw insertion, fluoroscopic images were taken and later analyzed to measure gap reduction. The effect of backing the screw out after compression was evaluated. Drilling at least 4 mm past the fracture site reduces distal fragment push-off compared with drilling only through the proximal fragment. There were no significant differences in gap closure in the normal versus the osteoporotic model. The Micro screw had a smaller gap closure than both the Standard and the Mini screws. After block contact and compression with 2 subsequent full forward turns, backing the screw out by only 1 full turn resulted in gapping between the blocks. Intuitively, fully threaded headless variable-pitch screws can obtain compression between bone fragments only if the initial gap is less than the gap closed. Gap closure may be affected by drilling technique, screw size, and screw length. Fragment compression may be immediately lost if the screw is reversed. We describe characteristics of variable-pitch headless screws that may assist the surgeon in screw choice and method of use. Copyright © 2018 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Acid-resistant calcium silicate-based composite implants with high-strength as load-bearing bone graft substitutes and fracture fixation devices.

PubMed

Wei, Chung-Kai; Ding, Shinn-Jyh

2016-09-01

To achieve the excellent mechanical properties of biodegradable materials used for cortical bone graft substitutes and fracture fixation devices remains a challenge. To this end, the biomimetic calcium silicate/gelatin/chitosan oligosaccharide composite implants were developed, with an aim of achieving high strength, controlled degradation, and superior osteogenic activity. The work focused on the effect of gelatin on mechanical properties of the composites under four different kinds of mechanical stresses including compression, tensile, bending, and impact. The evaluation of in vitro degradability and fatigue at two simulated body fluid (SBF) of pH 7.4 and 5.0 was also performed, in which the pH 5.0 condition simulated clinical conditions caused by bacterial induced local metabolic acidosis or tissue inflammation. In addition, human mesenchymal stem cells (hMSCs) were sued to examine osteogenic activity. Experimental results showed that the appropriate amount of gelatin positively contributed to failure enhancement in compressive and impact modes. The 10wt% gelatin-containing composite exhibits the maximum value of the compressive strength (166.1MPa), which is within the reported compressive strength for cortical bone. The stability of the bone implants was apparently affected by the in vitro fatigue, but not by the initial pH environments (7.4 or 5.0). The gelatin not only greatly enhanced the degradation of the composite when soaked in the dynamic SBF solution, but effectively promoted attachment, proliferation, differentiation, and formation of mineralization of hMSCs. The 10wt%-gelatin composite with high initial strength may be a potential implant candidate for cortical bone repair and fracture fixation applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Plantar Plating for the Treatment of Proximal Fifth Metatarsal Fractures in Elite Athletes.

PubMed

Mitchell, Ronald J; Duplantier, Neil L; Delgado, Domenica A; Lambert, Bradley S; McCulloch, Patrick C; Harris, Joshua D; Varner, Kevin E

2017-05-01

Proximal fifth metatarsal fractures, zones II and III, are commonly treated surgically, especially in elite athletes. Intramedullary screw fixation remains the most used construct despite nonunion and refracture. High tensile forces on the plantar-lateral aspect of the fifth metatarsal are difficult to control, and intramedullary screw fixation depends on ideal screw position, length, and width. The authors present a plantar plating technique with cancellous bone autograft for zones II and III proximal fifth metatarsal fractures. Rotational instability and plantar-lateral gapping are resisted by applying a compression plate to the tension side of the fracture, eliminating causes for failure. [Orthopedics. 2017; 40(3):e563-e566.]. Copyright 2017, SLACK Incorporated.

Using Fully Coupled Hydro-Geomechanical Numerical Test Bed to Study Reservoir Stimulation with Low Hydraulic Pressure

DOE Data Explorer

Fu, Pengcheng; Johnson, Scott M.; Carrigan, Charles R.

2012-01-31

This paper documents our effort to use a fully coupled hydro-geomechanical numerical test bed to study using low hydraulic pressure to stimulate geothermal reservoirs with existing fracture network. In this low pressure stimulation strategy, fluid pressure is lower than the minimum in situ compressive stress, so the fractures are not completely open but permeability improvement can be achieved through shear dilation. We found that in this low pressure regime, the coupling between the fluid phase and the rock solid phase becomes very simple, and the numerical model can achieve a low computational cost. Using this modified model, we study the behavior of a single fracture and a random fracture network.

Metal plasticity and ductile fracture modeling for cast aluminum alloy parts

DOE PAGES

Lee, Jinwoo; Kim, Se-Jong; Park, Hyeonil; ...

2018-01-06

Here in this study, plasticity and ductile fracture properties were characterized by performing various tension, shear, and compression tests. A series of 10 experiments were performed using notched round bars, flat-grooved plates, in-plane shear plates, and cylindrical bars. Two cast aluminum alloys used in automotive suspension systems were selected. Plasticity modelling was performed and the results were compared with experimental and corresponding simulation results; further, the relationships among the stress triaxiality, Lode angle parameter, and equivalent plastic strain at the onset of failure were determined to calibrate a ductile fracture model. Finally, the proposed ductile fracture model shows good agreementmore » with experimental results.« less

Classification and treatment of periprosthetic supracondylar femur fractures.

PubMed

Ricci, William

2013-02-01

Locked plating and retrograde nailing are two accepted methods for treatment of periprosthetic distal femur fractures. Each has relative benefits and potential pitfalls. Appropriate patient selection and knowledge of the specific femoral component geometry are required to optimally choose between these two methods. Locked plating may be applied to most periprosthetic distal femur fractures. The fracture pattern, simple or comminuted, will dictate the specific plating technique, compression plating or bridge plating. Nailing requires an open intercondylar box and a distal fragment of enough size to allow interlocking. With proper patient selection and proper techniques, good results can be obtained with either method. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Metal plasticity and ductile fracture modeling for cast aluminum alloy parts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jinwoo; Kim, Se-Jong; Park, Hyeonil

Here in this study, plasticity and ductile fracture properties were characterized by performing various tension, shear, and compression tests. A series of 10 experiments were performed using notched round bars, flat-grooved plates, in-plane shear plates, and cylindrical bars. Two cast aluminum alloys used in automotive suspension systems were selected. Plasticity modelling was performed and the results were compared with experimental and corresponding simulation results; further, the relationships among the stress triaxiality, Lode angle parameter, and equivalent plastic strain at the onset of failure were determined to calibrate a ductile fracture model. Finally, the proposed ductile fracture model shows good agreementmore » with experimental results.« less

Fracking and labquakes

NASA Astrophysics Data System (ADS)

Baró, Jordi; Planes, Antoni; Salje, Ekhard K. H.; Vives, Eduard

2016-12-01

Local fracture events (or labquakes) during compression of shale rocks have been studied by acoustic emission. They are assumed to simulate quakes induced by hydraulic fracturing (fracking) or other water injection activities. Results are compared with those obtained during compression of porous Vycor glass, which are known to display statistical features very similar to those characterising natural earthquakes. Our acoustic emission results show that labquake energies are power law distributed, which is consistent with recent statistical analysis of fracking-/water injection-induced quakes. The data confirm a Gutenberg-Richter behaviour with exponents larger than the exponents characterising the energy distribution of natural earthquakes. In contrast to natural earthquakes, labquakes in shales do not show time correlations, which indicates that the probability of aftershocks is smaller than in the natural scenario (e.g. during Californian earthquakes).

[Fractures of the lower leg in professional skiers].

PubMed

Mückley, T; Kruis, C; Schütz, T; Brucker, P; Bühren, V

2004-03-01

Fractures of the lower leg due to skiing accidents remain an important concern. Few studies have focussed on the special demands of professional athletes who sustain these injuries. We present our experience with three cases of lower leg fractures in competitive professional downhill skiers and discuss management and treatment concepts. We performed limited reamed compression nailing in all the patients presented because it offers the advantages of high mechanical stability and optimized fragment apposition. Plate osteosynthesis of the fibula is not required in most typical fractures. All patients resumed ski training. Two of them returned to World Cup. Only one achieved her pre-injury World Cup level of performance and success. In conclusion, a successful return for professional skiers with lower leg fractures is feasible using an optimized treatment strategy.

Effect of phenylephrine bolus administration on left ventricular function during postural hypotension in anesthetized patients.

PubMed

Goertz, A W; Schmidt, M; Lindner, K H; Seefelder, C; Georgieff, M

1993-01-01

To investigate the effect of intravenous (IV) phenylephrine (PHE) bolus administration on left ventricular function in patients who developed postural hypotension during isoflurane anesthesia in the head-up tilt (reverse Trendelenburg) position. Prospective "before-after" trial. Operation theater of a university medical center. 15 ASA physical status I and II patients without cardiovascular disorders. The anesthetized patients were tilted from a supine horizontal to a 30-degree reverse-Trendelenburg position. Once a steady state was achieved, PHE 3 micrograms/kg was administered as an IV bolus dose. Transesophageal echocardiography was used to assess left ventricular function. We measured blood pressure (BP); heart rate; left ventricular end-systolic and end-diastolic area, diameter, and wall thickness; and ejection time at baseline and after tilt, immediately before and for a period of 3 minutes after PHE injection. We calculated fractional area change (FAC), mean velocity of circumferential fiber shortening (mVcf), and end-systolic wall stress. Head-up tilt caused a reduction of mean arterial pressure [from 68 to 54 mmHg (mean)], end-systolic and end-diastolic left ventricular area (from 9.7 to 6.5 cm2 and from 19.2 to 13.1 cm2, respectively) and end-systolic wall stress (from 56 to 33 10(3).dyne/cm2). FAC and mVcf remained unaltered. PHE administration restored baseline values or overcompensated the changes caused by tilt. FAC slightly decreased in response to PHE (from 0.51 to 0.43), end-systolic wall stress increased to 83 10(3).dyne/cm2, and mVcf remained unchanged. PHE bolus administration effectively restored BP and cardiac filling, which were reduced after head-up tilt, without causing a relevant impairment of left ventricular function or an increase in end-systolic wall stress above the upper normal limit.

Permeability Changes in Reaction Induced Fracturing

NASA Astrophysics Data System (ADS)

Ulven, Ole Ivar; Malthe-Sørenssen, Anders; Kalia, Rajiv

2013-04-01

The process of fracture formation due to a volume increasing chemical reaction has been studied in a variety of different settings, e.g. weathering of dolerites by Røyne et al.[4], serpentinization and carbonation of peridotite by Rudge et al.[3] and replacement reactions in silica-poor igneous rocks by Jamtveit et al.[1]. It is generally assumed that fracture formation will increase the net permeability of the rock, and thus increase the reactant transport rate and subsequently the total reaction rate, as summarised by Kelemen et al.[2]. Røyne et al.[4] have shown that transport in fractures will have an effect on the fracture pattern formed. Understanding the feedback process between fracture formation and permeability changes is essential in assessing industrial scale CO2 sequestration in ultramafic rock, but little is seemingly known about how large the permeability change will be in reaction-induced fracturing under compression, and it remains an open question how sensitive a fracture pattern is to permeability changes. In this work, we study the permeability of fractures formed under compression, and we use a 2D discrete element model to study the fracture patterns and total reaction rates achieved with different permeabilities. We achieve an improved understanding of the feedback processes in reaction-driven fracturing, thus improving our ability to decide whether industrial scale CO2 sequestration in ultramafic rock is a viable option for long-term handling of CO2. References [1] Jamtveit, B, Putnis, C. V., and Malthe-Sørenssen, A., "Reaction induced fracturing during replacement processes," Contrib. Mineral Petrol. 157, 2009, pp. 127 - 133. [2] Kelemen, P., Matter, J., Streit, E. E., Rudge, J. F., Curry, W. B., and Blusztajn, J., "Rates and Mechanisms of Mineral Carbonation in Peridotite: Natural Processes and Recipes for Enhanced, in situ CO2 Capture and Storage," Annu. Rev. Earth Planet. Sci. 2011. 39:545-76. [3] Rudge, J. F., Kelemen, P. B., and Spiegelman, M., "A simple model of reaction induced cracking applied to serpentinization and carbonation of peridotite," Earth Planet. Sci. Lett. 291, Issues 1-4, 2010, pp. 215 - 227. [4] Røyne, A., Jamtveit, B., and Malthe-Sørenssen, A., "Controls on rock weathering rates by reaction-induced hierarchial fracturing," Earth Planet. Sci. Lett. 275, 2008, pp. 364 - 369.

Tectonic Setting and Characteristics of Natural Fractures in MesaVerde and Dakota Reservoirs of the San Juan Basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

LORENZ,JOHN C.; COOPER,SCOTT P.

2000-12-20

The Cretaceous strata that fill the San Juan Basin of northwestern New Mexico and southwestern Colorado were shortened in a generally N-S to NN13-SSW direction during the Laramide orogeny. This shortening was the result of compression of the strata between southward indentation of the San Juan Uplift at the north edge of the basin and northward to northeastward indentation of the Zuni Uplift from the south. Right-lateral strike-slip motion was concentrated at the eastern and western basin margins of the basin to form the Hogback Monocline and the Nacimiento Uplift at the same time, and small amounts of shear maymore » have been pervasive within the basin as well. Vertical extension fractures, striking N-S to NNE-SSW with local variations (parallel to the Laramide maximum horizontal compressive stress), formed in both Mesaverde and Dakota sandstones under this system, and are found in outcrops and in the subsurface of the San Juan Basin. The immature Mesaverde sandstones typically contain relatively long, irregular, vertical extension fractures, whereas the quartzitic Dakota sandstones contain more numerous, shorter, sub-parallel, closely spaced, extension fractures. Conjugate shear planes in several orientations are also present locally in the Dakota strata.« less

Laboratory hydraulic fracturing experiments in intact and pre-fractured rock

USGS Publications Warehouse

Zoback, M.D.; Rummel, F.; Jung, R.; Raleigh, C.B.

1977-01-01

Laboratory hydraulic fracturing experiments were conducted to investigate two factors which could influence the use of the hydrofrac technique for in-situ stress determinations; the possible dependence of the breakdown pressure upon the rate of borehole pressurization, and the influence of pre-existing cracks on the orientation of generated fractures. The experiments have shown that while the rate of borehole pressurization has a marked effect on breakdown pressures, the pressure at which hydraulic fractures initiate (and thus tensile strength) is independent of the rate of borehole pressurization when the effect of fluid penetration is negligible. Thus, the experiments indicate that use of breakdown pressures rather than fracture initiation pressures may lead to an erroneous estimate of tectonic stresses. A conceptual model is proposed to explain anomalously high breakdown pressures observed when fracturing with high viscosity fluids. In this model, initial fracture propagation is presumed to be stable due to large differences between the borehole pressure and that within the fracture. In samples which contained pre-existing fractures which were 'leaky' to water, we found it possible to generate hydraulic fractures oriented parallel to the direction of maximum compression if high viscosity drilling mud was used as the fracturing fluid. ?? 1977.

Fracture-permeability behavior of shale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carey, J. William; Lei, Zhou; Rougier, Esteban

The fracture-permeability behavior of Utica shale, an important play for shale gas and oil, was investigated using a triaxial coreflood device and X-ray tomography in combination with finite-discrete element modeling (FDEM). Fractures generated in both compression and in a direct-shear configuration allowed permeability to be measured across the faces of cylindrical core. Shale with bedding planes perpendicular to direct-shear loading developed complex fracture networks and peak permeability of 30 mD that fell to 5 mD under hydrostatic conditions. Shale with bedding planes parallel to shear loading developed simple fractures with peak permeability as high as 900 mD. In addition tomore » the large anisotropy in fracture permeability, the amount of deformation required to initiate fractures was greater for perpendicular layering (about 1% versus 0.4%), and in both cases activation of existing fractures are more likely sources of permeability in shale gas plays or damaged caprock in CO₂ sequestration because of the significant deformation required to form new fracture networks. FDEM numerical simulations were able to replicate the main features of the fracturing processes while showing the importance of fluid penetration into fractures as well as layering in determining fracture patterns.« less

Fracture-permeability behavior of shale

DOE PAGES

Carey, J. William; Lei, Zhou; Rougier, Esteban; ...

2015-05-08

The fracture-permeability behavior of Utica shale, an important play for shale gas and oil, was investigated using a triaxial coreflood device and X-ray tomography in combination with finite-discrete element modeling (FDEM). Fractures generated in both compression and in a direct-shear configuration allowed permeability to be measured across the faces of cylindrical core. Shale with bedding planes perpendicular to direct-shear loading developed complex fracture networks and peak permeability of 30 mD that fell to 5 mD under hydrostatic conditions. Shale with bedding planes parallel to shear loading developed simple fractures with peak permeability as high as 900 mD. In addition tomore » the large anisotropy in fracture permeability, the amount of deformation required to initiate fractures was greater for perpendicular layering (about 1% versus 0.4%), and in both cases activation of existing fractures are more likely sources of permeability in shale gas plays or damaged caprock in CO₂ sequestration because of the significant deformation required to form new fracture networks. FDEM numerical simulations were able to replicate the main features of the fracturing processes while showing the importance of fluid penetration into fractures as well as layering in determining fracture patterns.« less

Simulating Fragmentation and Fluid-Induced Fracture in Disordered Media Using Random Finite-Element Meshes

DOE PAGES

Bishop, Joseph E.; Martinez, Mario J.; Newell, Pania

2016-11-08

Fracture and fragmentation are extremely nonlinear multiscale processes in which microscale damage mechanisms emerge at the macroscale as new fracture surfaces. Numerous numerical methods have been developed for simulating fracture initiation, propagation, and coalescence. In this paper, we present a computational approach for modeling pervasive fracture in quasi-brittle materials based on random close-packed Voronoi tessellations. Each Voronoi cell is formulated as a polyhedral finite element containing an arbitrary number of vertices and faces. Fracture surfaces are allowed to nucleate only at the intercell faces. Cohesive softening tractions are applied to new fracture surfaces in order to model the energy dissipatedmore » during fracture growth. The randomly seeded Voronoi cells provide a regularized discrete random network for representing fracture surfaces. The potential crack paths within the random network are viewed as instances of realizable crack paths within the continuum material. Mesh convergence of fracture simulations is viewed in a weak, or distributional, sense. The explicit facet representation of fractures within this approach is advantageous for modeling contact on new fracture surfaces and fluid flow within the evolving fracture network. Finally, applications of interest include fracture and fragmentation in quasi-brittle materials and geomechanical applications such as hydraulic fracturing, engineered geothermal systems, compressed-air energy storage, and carbon sequestration.« less

Simulating Fragmentation and Fluid-Induced Fracture in Disordered Media Using Random Finite-Element Meshes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, Joseph E.; Martinez, Mario J.; Newell, Pania

Fracture and fragmentation are extremely nonlinear multiscale processes in which microscale damage mechanisms emerge at the macroscale as new fracture surfaces. Numerous numerical methods have been developed for simulating fracture initiation, propagation, and coalescence. In this paper, we present a computational approach for modeling pervasive fracture in quasi-brittle materials based on random close-packed Voronoi tessellations. Each Voronoi cell is formulated as a polyhedral finite element containing an arbitrary number of vertices and faces. Fracture surfaces are allowed to nucleate only at the intercell faces. Cohesive softening tractions are applied to new fracture surfaces in order to model the energy dissipatedmore » during fracture growth. The randomly seeded Voronoi cells provide a regularized discrete random network for representing fracture surfaces. The potential crack paths within the random network are viewed as instances of realizable crack paths within the continuum material. Mesh convergence of fracture simulations is viewed in a weak, or distributional, sense. The explicit facet representation of fractures within this approach is advantageous for modeling contact on new fracture surfaces and fluid flow within the evolving fracture network. Finally, applications of interest include fracture and fragmentation in quasi-brittle materials and geomechanical applications such as hydraulic fracturing, engineered geothermal systems, compressed-air energy storage, and carbon sequestration.« less

Effect of interfragmentary gap on compression force in a headless compression screw used for scaphoid fixation.

PubMed

Tan, E S; Mat Jais, I S; Abdul Rahim, S; Tay, S C

2018-01-01

We investigated the effect of an interfragmentary gap on the final compression force using the Acutrak 2 Mini headless compression screw (length 26 mm) (Acumed, Hillsboro, OR, USA). Two blocks of solid rigid polyurethane foam in a custom jig were separated by spacers of varying thickness (1.0, 1.5, 2.0 and 2.5 mm) to simulate an interfragmentary gap. The spacers were removed before full insertion of the screw and the compression force was measured when the screw was buried 2 mm below the surface of the upper block. Gaps of 1.5 mm and 2.0 mm resulted in significantly decreased compression forces, whereas there was no significant decrease in compression force with a gap of 1 mm. An interfragmentary gap of 2.5 mm did not result in any contact between blocks. We conclude that an increased interfragmentary gap leads to decreased compression force with this screw, which may have implications on fracture healing.

Multiporosity flow in fractured low-permeability rocks: Extension to shale hydrocarbon reservoirs

DOE PAGES

Kuhlman, Kristopher L.; Malama, Bwalya; Heath, Jason E.

2015-02-05

We presented a multiporosity extension of classical double and triple-porosity fractured rock flow models for slightly compressible fluids. The multiporosity model is an adaptation of the multirate solute transport model of Haggerty and Gorelick (1995) to viscous flow in fractured rock reservoirs. It is a generalization of both pseudo steady state and transient interporosity flow double-porosity models. The model includes a fracture continuum and an overlapping distribution of multiple rock matrix continua, whose fracture-matrix exchange coefficients are specified through a discrete probability mass function. Semianalytical cylindrically symmetric solutions to the multiporosity mathematical model are developed using the Laplace transform tomore » illustrate its behavior. Furthermore, the multiporosity model presented here is conceptually simple, yet flexible enough to simulate common conceptualizations of double and triple-porosity flow. This combination of generality and simplicity makes the multiporosity model a good choice for flow modelling in low-permeability fractured rocks.« less

Experimental investigation of mode I fracture for brittle tube-shaped particles

NASA Astrophysics Data System (ADS)

Stasiak, Marta; Combe, Gaël; Desrues, Jacques; Richefeu, Vincent; Villard, Pascal; Armand, Gilles; Zghondi, Jad

2017-06-01

We focus herein on the mechanical behavior of highly crushable grains. The object of our interest, named shell, is a hollow cylinder grain with ring cross-section, made of baked clay. The objective is to model the fragmentation of such shells, by means of discrete element (DE) approach. To this end, fracture modes I (opening fracture) and II (in-plane shear fracture) have to be investigated experimentally. This paper is essentially dedicated to mode I fracture. Therefore, a campaign of Brazilian-like compression tests, that result in crack opening, has been performed. The distribution of the occurrence of tensile strength is shown to obey a Weibull distribution for the studied shells, and Weibull's modulus was quantified. Finally, an estimate of the numerical/physical parameters required in a DE model (local strength), is proposed on the basis of the energy required to fracture through a given surface in mode I or II.

Compressive Deformation Behavior of Closed-Cell Micro-Pore Magnesium Composite Foam.

PubMed

Wang, Jing; Wang, Nannan; Liu, Xin; Ding, Jian; Xia, Xingchuan; Chen, Xueguang; Zhao, Weimin

2018-05-04

The closed-cell micro-pore magnesium composite foam with hollow ceramic microspheres (CMs) was fabricated by a modified melt foaming method. The effect of CMs on the compressive deformation behavior of CM-containing magnesium composite foam was investigated. Optical microscopy and scanning electron microscopy were used for observation of the microstructure. Finite element modeling of the magnesium composite foam was established to predict localized stress, fracture of CMs, and the compressive deformation behavior of the foam. The results showed that CMs and pores directly affected the compressive deformation behavior of the magnesium composite foam by sharing a part of load applied on the foam. Meanwhile, the presence of Mg₂Si phase influenced the mechanical properties of the foam by acting as the crack source during the compression process.

Compressive Deformation Behavior of Closed-Cell Micro-Pore Magnesium Composite Foam

PubMed Central

Wang, Jing; Wang, Nannan; Liu, Xin; Ding, Jian; Xia, Xingchuan; Chen, Xueguang; Zhao, Weimin

2018-01-01

The closed-cell micro-pore magnesium composite foam with hollow ceramic microspheres (CMs) was fabricated by a modified melt foaming method. The effect of CMs on the compressive deformation behavior of CM-containing magnesium composite foam was investigated. Optical microscopy and scanning electron microscopy were used for observation of the microstructure. Finite element modeling of the magnesium composite foam was established to predict localized stress, fracture of CMs, and the compressive deformation behavior of the foam. The results showed that CMs and pores directly affected the compressive deformation behavior of the magnesium composite foam by sharing a part of load applied on the foam. Meanwhile, the presence of Mg2Si phase influenced the mechanical properties of the foam by acting as the crack source during the compression process. PMID:29734700

Transverse stresses and modes of failure in tree branches and other beams

PubMed Central

Ennos, A. R.; van Casteren, A.

2010-01-01

The longitudinal stresses in beams subjected to bending also set up transverse stresses within them; they compress the cross section when the beam's curvature is being increased and stretch it when its curvature is being reduced. Analysis shows that transverse stresses rise to a maximum at the neutral axis and increase with both the bending moment applied and the curvature of the beam. These stresses can qualitatively explain the fracture behaviour of tree branches. Curved ‘hazard beams’ that are being straightened split down the middle because of the low transverse tensile strength of wood. By contrast, straight branches of light wood buckle when they are bent because of its low transverse compressive strength. Branches of denser wood break, but the low transverse tensile strength diverts the crack longitudinally when the fracture has only run half-way across the beam, to produce their characteristic ‘greenstick fracture’. The bones of young mammals and uniaxially reinforced composite beams may also be prone to greenstick fracture because of their lower transverse tensile strength. PMID:20018786

Strengthening of Aluminum Alloy 2219 by Thermo-mechanical Treatment

NASA Astrophysics Data System (ADS)

Li, Xifeng; Lei, Kun; Song, Peng; Liu, Xinqin; Zhang, Fei; Li, Jianfei; Chen, Jun

2015-10-01

Strengthening of aluminum alloy 2219 by thermo-mechanical treatment has been compared with artificial aging. Three simple deformation modes including pre-stretching, compression, and rolling have been used in thermo-mechanical treatment. The tensile strength, elongation, fracture feature, and precipitated phase have been investigated. The results show that the strengthening effect of thermo-mechanical treatment is better than the one of artificial aging. Especially, the yield strength significantly increases with a small decrease of elongation. When the specimen is pre-stretched to 8.0%, the yield strength reaches 385.0 MPa and increases by 22.2% in comparison to the one obtained in aging condition. The maximum tensile strength of 472.4 MPa is achieved with 4.0% thickness reduction by compression. The fracture morphology reveals locally ductile and brittle failure mechanism, while the coarse second-phase particles distribute on the fracture surface. The intermediate phases θ″ or θ' orthogonally precipitate in the matrix after thermo-mechanical treatment. As compared to artificial aging, the cold plastic deformation increases distribution homogeneity and the volume fraction of θ'' or θ' precipitates. These result in a better strengthening effect.

Strength and fracture mechanism of iron reinforced tricalcium phosphate cermet fabricated by spark plasma sintering.

PubMed

Tkachenko, Serhii; Horynová, Miroslava; Casas-Luna, Mariano; Diaz-de-la-Torre, Sebastian; Dvořák, Karel; Celko, Ladislav; Kaiser, Jozef; Montufar, Edgar B

2018-05-01

The present work studies the microstructure and mechanical performance of tricalcium phosphate (TCP) based cermet toughened by iron particles. A novelty arises by the employment of spark plasma sintering for fabrication of the cermet. Results showed partial transformation of initial alpha TCP matrix to beta phase and the absence of oxidation of iron particles, as well as a lack of chemical reaction between TCP and iron components during sintering. The values of compressive and tensile strength of TCP/Fe cermet were 3.2 and 2.5 times, respectively, greater than those of monolithic TCP. Fracture analysis revealed the simultaneous action of crack-bridging and crack-deflection microstructural toughening mechanisms under compression. In contrast, under tension the reinforcing mechanism was only crack-bridging, being the reason for smaller increment of strength. Elastic properties of the cermet better matched values reported for human cortical bone. Thereby the new TCP/Fe cermet has potential for eventual use as a material for bone fractures fixation under load-bearing conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Finite element model for brittle fracture and fragmentation

DOE PAGES

Li, Wei; Delaney, Tristan J.; Jiao, Xiangmin; ...

2016-06-01

A new computational model for brittle fracture and fragmentation has been developed based on finite element analysis of non-linear elasticity equations. The proposed model propagates the cracks by splitting the mesh nodes alongside the most over-strained edges based on the principal direction of strain tensor. To prevent elements from overlapping and folding under large deformations, robust geometrical constraints using the method of Lagrange multipliers have been incorporated. In conclusion, the model has been applied to 2D simulations of the formation and propagation of cracks in brittle materials, and the fracture and fragmentation of stretched and compressed materials.

Finite element model for brittle fracture and fragmentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Wei; Delaney, Tristan J.; Jiao, Xiangmin

A new computational model for brittle fracture and fragmentation has been developed based on finite element analysis of non-linear elasticity equations. The proposed model propagates the cracks by splitting the mesh nodes alongside the most over-strained edges based on the principal direction of strain tensor. To prevent elements from overlapping and folding under large deformations, robust geometrical constraints using the method of Lagrange multipliers have been incorporated. In conclusion, the model has been applied to 2D simulations of the formation and propagation of cracks in brittle materials, and the fracture and fragmentation of stretched and compressed materials.

Melt fracture revisited

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenberg, J. M.

2003-07-16

In a previous paper the author and Demay advanced a model to explain the melt fracture instability observed when molten linear polymer melts are extruded in a capillary rheometer operating under the controlled condition that the inlet flow rate was held constant. The model postulated that the melts were a slightly compressible viscous fluid and allowed for slipping of the melt at the wall. The novel feature of that model was the use of an empirical switch law which governed the amount of wall slip. The model successfully accounted for the oscillatory behavior of the exit flow rate, typically referredmore » to as the melt fracture instability, but did not simultaneously yield the fine scale spatial oscillations in the melt typically referred to as shark skin. In this note a new model is advanced which simultaneously explains the melt fracture instability and shark skin phenomena. The model postulates that the polymer is a slightly compressible linearly viscous fluid but assumes no slip boundary conditions at the capillary wall. In simple shear the shear stress {tau}and strain rate d are assumed to be related by d = F{tau} where F ranges between F{sub 2} and F{sub 1} > F{sub 2}. A strain rate dependent yield function is introduced and this function governs whether F evolves towards F{sub 2} or F{sub 1}. This model accounts for the empirical observation that at high shears polymers align and slide more easily than at low shears and explains both the melt fracture and shark skin phenomena.« less

Finite Element Analysis of Aluminum Honeycombs Subjected to Dynamic Indentation and Compression Loads

PubMed Central

Ashab, A.S.M. Ayman; Ruan, Dong; Lu, Guoxing; Bhuiyan, Arafat A.

2016-01-01

The mechanical behavior of aluminum hexagonal honeycombs subjected to out-of-plane dynamic indentation and compression loads has been investigated numerically using ANSYS/LS-DYNA in this paper. The finite element (FE) models have been verified by previous experimental results in terms of deformation pattern, stress-strain curve, and energy dissipation. The verified FE models have then been used in comprehensive numerical analysis of different aluminum honeycombs. Plateau stress, σpl, and dissipated energy (EI for indentation and EC for compression) have been calculated at different strain rates ranging from 102 to 104 s−1. The effects of strain rate and t/l ratio on the plateau stress, dissipated energy, and tearing energy have been discussed. An empirical formula is proposed to describe the relationship between the tearing energy per unit fracture area, relative density, and strain rate for honeycombs. Moreover, it has been found that a generic formula can be used to describe the relationship between tearing energy per unit fracture area and relative density for both aluminum honeycombs and foams. PMID:28773288

Bilateral orbital emphysema and pneumocephalus as a result of accidental compressed air exposure.

PubMed

Yuksel, Murvet; Yuksel, K Zafer; Ozdemir, Gokhan; Ugur, Tuncay

2007-01-01

Orbital emphysema is a rare condition in the absence of trauma or sinus disease. A 22-year-old man suffering from left orbital trauma due to sudden exposure to compressed air tube was admitted with severe pain in the left eye, swelling, and mild periorbital ecchymosis. Physical examination revealed a large conjunctival laceration in the left orbit. Multislice computed tomographic scanning of the head and orbits showed extensive radiolucencies consistent with the air in both orbits, more prominent in the left. There was also subcutaneous air in the left periorbital soft tissue extending through fronto-temporal and zygomatic areas. Air was also demonstrated adjacent to the left optic canal and within the subarachnoid space intracranially. There was no evidence of any orbital, paranasal sinus, or cranial fracture. Visual acuity was minimally decreased bilaterally. The conjunctiva was sutured under local anesthesia. After 3 weeks of follow-up, the patient completely recovered without visual loss. Bilateral orbital emphysema with pneumocephalus can occur from a high-pressure compressed air injury after unilateral conjunctival trauma without any evidence of fracture.

3D finite element modelling of force transmission and particle fracture of sand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imseeh, Wadi H.; Alshibli, Khalid A.

Global compressive loading of granular media causes rearrangements of particles into a denser configuration. Under 1D compression, researchers observed that particles initially translate and rotate which lead to more contacts between particles and the development of force chains to resist applied loads. Particles within force chains resist most of the applied loads while neighbor particles provide lateral support to prevent particles within force chains from buckling. Several experimental and numerical models have been proposed in the literature to characterize force chains within granular materials. This paper presents a 3D finite element (FE) model that simulates 1D compression experiment on F-75more » Ottawa sand. The FE mesh of particles closely matched 3D physical shape of sand particles that were acquired using 3D synchrotron micro-computed tomography (SMT) technique. The paper presents a quantitative assessment of the model, in which evolution of force chains, fracture modes, and stress-strain relationships showed an excellent agreement with experimental measurements reported by Cil et al. Alshibli (2017).« less

Microstructural effects on fracture toughness of polycrystalline ceramics in combined mode I and mode II loading

NASA Technical Reports Server (NTRS)

Singh, D.; Shetty, D. K.

1988-01-01

Fracture toughness of polycrystalline alumina and ceria partially-stabilized tetragonal zirconia (CeO2-TZP) ceramics were assessed in combined mode I and mode II loading using precracked disk specimens in diametral compression. Stress states ranging from pure mode I, combined mode I and mode II, and pure mode II were obtained by aligning the center crack at specific angles relative to the loading diameter. The resulting mixed-mode fracture toughness envelope showed significant deviation to higher fracture toughness in mode II relative to the predictions of the linear elastic fracture mechanics theory. Critical comparison with corresponding results on soda-lime glass and fracture surface observations showed that crack surface resistance arising from grain interlocking and abrasion was the main source of the increased fracture toughness in mode II loading of the polycrystalline ceramics. The normalized fracture toughness for pure mode II loading, (KII/KIc), increased with increasing grain size for the CeO2-TZP ceramics. Quantitative fractography confirmed an increased percentage of transgranular fracture of the grains in mode II loading.

In vitro study of fracture load and fracture pattern of ceramic crowns: a finite element and fractography analysis.

PubMed

Campos, Roberto Elias; Soares, Carlos José; Quagliatto, Paulo S; Soares, Paulo Vinícius; de Oliveira, Osmir Batista; Santos-Filho, Paulo Cesar Freitas; Salazar-Marocho, Susana M

2011-08-01

This in vitro study investigated the null hypothesis that metal-free crowns induce fracture loads and mechanical behavior similar to metal ceramic systems and to study the fracture pattern of ceramic crowns under compressive loads using finite element and fractography analyses. Six groups (n = 8) with crowns from different systems were compared: conventional metal ceramic (Noritake) (CMC); modified metal ceramic (Noritake) (MMC); lithium disilicate-reinforced ceramic (IPS Empress II) (EMP); leucite-reinforced ceramic (Cergogold) (CERG); leucite fluoride-apatite reinforced ceramic (IPS d.Sign) (SIGN); and polymer crowns (Targis) (TARG). Standardized crown preparations were performed on bovine roots containing NiCr metal dowels and resin cores. Crowns were fabricated using the ceramics listed, cemented with dual-cure resin cement, and submitted to compressive loads in a mechanical testing machine at a 0.5-mm/min crosshead speed. Data were submitted to one-way ANOVA and Tukey tests, and fractured specimens were visually inspected under a stereomicroscope (20×) to determine the type of fracture. Maximum principal stress (MPS) distributions were calculated using finite element analysis, and fracture origin and the correlation with the fracture type were determined using fractography. Mean values of fracture resistance (N) for all groups were: CMC: 1383 ± 298 (a); MMC: 1691 ± 236 (a); EMP: 657 ± 153 (b); CERG: 546 ± 149 (bc); SIGN: 443 ± 126 (c); TARG: 749 ± 113 (b). Statistical results showed significant differences among groups (p < 0.05) represented by different lowercase letters. Metal ceramic crowns presented fracture loads significantly higher than the others. Ceramic specimens presented high incidence of fractures involving either the core or the tooth, and all fractures of polymer crown specimens involved the tooth in a catastrophic way. Based on stress and fractographic analyses it was determined that fracture occurred from the occlusal to the cervical direction. Within the limitations of this study, the results indicated that the use of ceramic and polymer crowns without a core reinforcement should be carefully evaluated before clinical use due to the high incidence of failure with tooth involvement. This mainly occurred for the polymer crown group, although the fracture load was higher than normal occlusal forces. High tensile stress concentrations were found around and between the occlusal loading points. Fractographic analysis indicated fracture originating from the load point and propagating from the occlusal surface toward the cervical area, which is the opposite direction of that observed in clinical situations. © 2011 by The American College of Prosthodontists.

Toughening of PMR composites by gradient semi-interpenetrating networks

NASA Technical Reports Server (NTRS)

Johnston, N. J.; Srinivasan, K.; Peter, R. H.

1992-01-01

The toughening of the PMR-15 and LARC RP-46 high temperature thermosetting polyimides is presently attempted through the construction of a semiinterpenetrating network at ply interfaces through the use of the Matrimid 5218 thermoplastic polyimide powder, whose 315-320 glass transition temperature is compatible with the PMR matrices. The 60 vol pct fiber composites thus prepared for the two resins, with and without toughening, were comprehensively characterized in flexure, tension, intralaminar and short beam shear, compression and quasi-isotropic short-block compression, as well as modes I and II interlaminar fracture toughness and compression after impact.

Planning for Program Design and Assessment Using Value Creation Frameworks

ERIC Educational Resources Information Center

Whisler, Laurel; Anderson, Rachel; Brown, Jenai

2017-01-01

This article explains a program design and planning process using the Value Creation Framework (VCF) developed by Wenger, Trayner, and de Laat (2011). The framework involves identifying types of value or benefit for those involved in the program, conditions and activities that support creation of that value, data that measure whether the value was…

Decreased fracture rate, pharmacogenetics and BMD response in 79 Swedish children with osteogenesis imperfecta types I, III and IV treated with Pamidronate.

PubMed

Lindahl, K; Kindmark, A; Rubin, C-J; Malmgren, B; Grigelioniene, G; Söderhäll, S; Ljunggren, Ö; Åström, E

2016-06-01

Osteogenesis imperfecta (OI) is an inherited heterogeneous bone fragility disorder, usually caused by collagen I mutations. It is well established that bisphosphonate treatment increases lumbar spine (LS) bone mineral density (BMD), as well as improves vertebral geometry in severe OI; however, fracture reduction has been difficult to prove, pharmacogenetic studies are scarce, and it is not known at which age, or severity of disease, treatment should be initiated. COL1A1 and COL1A2 were analyzed in 79 children with OI (type I n=33, type III n=25 and type IV n=21) treated with Pamidronate. Data on LS BMD, height, and radiologically confirmed non-vertebral and vertebral fractures were collected prior to, and at several time points during treatment. An increase in LS BMD Z-score was observed for all types of OI, and a negative correlation to Δ LS BMD was observed for both age and LS BMD Z-score at treatment initiation. Supine height Z-scores were not affected by Pamidronate treatment, The fracture rate was reduced for all OI types at all time points during treatment (overall p<0.0003, <0.0001 and 0.0003 for all OI types I, III and IV respectively). The reduced fracture rate was maintained for types I and IV, while an additional decrease was observed over time for type III. The fracture rate was reduced also in individuals with continued low BMD after >4yrs Pamidronate. Twice as many boys as girls with OI type I were treated with Pamidronate, and the fracture rate the year prior treatment was 2.2 times higher for boys (p=0.0236). Greater Δ LS BMD, but smaller Δ fracture numbers were observed on Pamidronate for helical glycine mutations in COL1A1 vs. COL1A2. Vertebral compression fractures did not progress in any individual during treatment; however, they did not improve in 9%, and these individuals were all >11years of age at treatment initiation (p<0.0001). Pamidronate treatment in children with all types of OI increased LS BMD, decreased fracture rate, and improved vertebral compression fractures. Fracture reduction was prompt and maintained during treatment, irrespective of age at treatment initiation and collagen I mutation type. Copyright © 2016 Elsevier Inc. All rights reserved.

Optimisation of composite bone plates for ulnar transverse fractures.

PubMed

Chakladar, N D; Harper, L T; Parsons, A J

2016-04-01

Metallic bone plates are commonly used for arm bone fractures where conservative treatment (casts) cannot provide adequate support and compression at the fracture site. These plates, made of stainless steel or titanium alloys, tend to shield stress transfer at the fracture site and delay the bone healing rate. This study investigates the feasibility of adopting advanced composite materials to overcome stress shielding effects by optimising the geometry and mechanical properties of the plate to match more closely to the bone. An ulnar transverse fracture is characterised and finite element techniques are employed to investigate the feasibility of a composite-plated fractured bone construct over a stainless steel equivalent. Numerical models of intact and fractured bones are analysed and the mechanical behaviour is found to agree with experimental data. The mechanical properties are tailored to produce an optimised composite plate, offering a 25% reduction in length and a 70% reduction in mass. The optimised design may help to reduce stress shielding and increase bone healing rates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Isolated displaced non-union of a triquetral body fracture: a case report

PubMed Central

2012-01-01

Introduction Fractures of the body of the triquetral bone are the second most common carpal fractures, and these fractures can be missed on plain X-ray. Although non-union of triquetral body fractures is very rare, such cases are associated with considerable morbidity and reduction in functional activity. Case presentation We report the case of a 29-year-old Caucasian British man who sustained an isolated displaced triquetral body fracture that resulted in non-union, who was treated surgically. We describe an original operative management for this debilitating injury. An open reduction and internal fixation using double headed compression screws was performed, without bone grafting, and with early immobilization of the wrist. Conclusions We propose this novel approach and advocate early clinical suspicion of triquetral body fractures in patients with a history of fall on an outstretched hand and ulnar sided wrist pain. We recommend evaluation using computed tomography or magnetic resonance imaging scanning. PMID:22325450

Biomechanical Comparison of Inter-fragmentary Compression Pressures: Lag Screw versus Herbert Screw for Anterior Odontoid Screw Fixation.

PubMed

Park, Jin-Woo; Kim, Kyoung-Tae; Sung, Joo-Kyung; Park, Seong-Hyun; Seong, Ki-Woong; Cho, Dae-Chul

2017-09-01

The purpose of the present study was to compare inter-fragmentary compression pressures after fixation of a simulated type II odontoid fracture with the headless compression Herbert screw and a half threaded cannulated lag screw. We compared inter-fragmentary compression pressures between 40- and 45-mm long 4.5-mm Herbert screws (n=8 and n=9, respectively) and 40- and 45-mm long 4.0-mm cannulated lag screws (n=7 and n=10, respectively) after insertion into rigid polyurethane foam test blocks (Sawbones, Vashon, WA, USA). A washer load cell was placed between the two segments of test blocks to measure the compression force. Because the total length of each foam block was 42 mm, the 40-mm screws were embedded in the cancellous foam, while the 45-mm screws penetrated the denser cortical foam at the bottom. This enabled us to compare inter-fragmentary compression pressures as they are affected by the penetration of the apical dens tip by the screws. The mean compression pressures of the 40- and 45-mm long cannulated lag screws were 50.48±1.20 N and 53.88±1.02 N, respectively, which was not statistically significant (p=0.0551). The mean compression pressures of the 40-mm long Herbert screw was 52.82±2.17 N, and was not statistically significant compared with the 40-mm long cannulated lag screw (p=0.3679). However, 45-mm Herbert screw had significantly higher mean compression pressure (60.68±2.03 N) than both the 45-mm cannulated lag screw and the 40-mm Herbert screw (p=0.0049 and p=0.0246, respectively). Our results showed that inter-fragmentary compression pressures of the Herbert screw were significantly increased when the screw tip penetrated the opposite dens cortical foam. This can support the generally recommended surgical technique that, in order to facilitate maximal reduction of the fracture gap using anterior odontoid screws, it is essential to penetrate the apical dens tip with the screw.

Bilateral simultaneous femoral neck and shafts fractures - a case report.

PubMed

Sadeghifar, Amirreza; Saied, Alireza

2014-10-01

Simultaneous fractures of the femoral neck and shaft are not common injuries, though they cannot be considered rare. Herein, we report our experience with a patient with bilateral occurance of this injury. Up to the best of our knowkedge this is the first case reported in literature in which correct diagnosis was made initially. Both femurs were fixed using broad 4.5 mm dynamic compression plate and both necks were fixed using 6.5 mm cannulated screws. Femur fixation on one side was converted to retrograde nailing because of plate failure. Both neck fractures healed uneventfully. In spite of rarity of concomitant fractures of femoral neck and shaft, this injury must be approached carefully demanding especial attention and careful device selection.

Seismic Attenuation and Stiffness Modulus Dispersion in Porous Rocks Containing Stochastic Fracture Networks

NASA Astrophysics Data System (ADS)

Hunziker, Jürg; Favino, Marco; Caspari, Eva; Quintal, Beatriz; Rubino, J. Germán.; Krause, Rolf; Holliger, Klaus

2018-01-01

Understanding seismic attenuation and modulus dispersion mechanisms in fractured rocks can result in significant advances for the indirect characterization of such environments. In this paper, we study attenuation and modulus dispersion of seismic waves caused by fluid pressure diffusion (FPD) in stochastic 2-D fracture networks, allowing for a state-of-the-art representation of natural fracture networks by a power law length distribution. To this end, we apply numerical upscaling experiments consisting of compression and shear tests to our samples of fractured rocks. The resulting P and S wave attenuation and modulus dispersion behavior is analyzed with respect to the density, the length distribution, and the connectivity of the fractures. We focus our analysis on two manifestations of FPD arising in fractured rocks, namely, fracture-to-background FPD at lower frequencies and fracture-to-fracture FPD at higher frequencies. Our results indicate that FPD is sensitive not only to the fracture density but also to the geometrical characteristics of the fracture length distributions. In particular, our study suggests that information about the local connectivity of a fracture network could be retrieved from seismic data. Conversely, information about the global connectivity, which is directly linked to the effective hydraulic conductivity of the probed volume, remains rather difficult to infer.

Hip fracture - discharge

MedlinePlus

... or a special metal plate or rod with screws, called compression screws or nails, put in place. Alternatively, you may ... walking as soon as possible. For this reason, it is very important to stay active and follow ...

The effect of the interaction of cracks in orthotropic layered materials under compressive loading.

PubMed

Winiarski, B; Guz, I A

2008-05-28

The non-classical problem of fracture mechanics of composites compressed along the layers with interfacial cracks is analysed. The statement of the problem is based on the model of piecewise homogeneous medium, the most accurate within the framework of the mechanics of deformable bodies as applied to composites. The condition of plane strain state is examined. The layers are modelled by a transversally isotropic material (a matrix reinforced by continuous parallel fibres). The frictionless Hertzian contact of the crack faces is considered. The complex fracture mechanics problem is solved using the finite-element analysis. The shear mode of stability loss is studied. The results are obtained for the typical dispositions of cracks. It was found that the interacting crack faces, the crack length and the mutual position of cracks influence the critical strain in the composite.

Delamination growth in composite materials

NASA Technical Reports Server (NTRS)

Gillespie, J. W., Jr.; Carlson, L. A.; Pipes, R. B.; Rothschilds, R.; Trethewey, B.; Smiley, A.

1985-01-01

Research related to growth of an imbedded through-width delamination (ITWD) in a compression loaded composite structural element is presented. Composites with widely different interlaminar fracture resistance were examined, viz., graphite/epoxy (CYCOM 982) and graphite/PEEK (APC-2). The initial part of the program consisted of characterizing the material in tension, compression and shear mainly to obtain consistent material properties for analysis, but also as a check of the processing method developed for the thermoplastic APC-2 material. The characterization of the delamination growth in the ITWD specimen, which for the unidirectional case is essentially a mixed Mode 1 and 2 geometry, requires verified mixed-mode growth criteria for the two materials involved. For this purpose the main emphasis during this part of the investigation was on Mode 1 and 2 fracture specimens, namely the Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimens.

Increased Antibiotic Release from a Bone Cement Containing Bacterial Cellulose

PubMed Central

Nakai, Takahisa; Enomoto, Koichi; Uchio, Yuji; Yoshino, Katsumi

2010-01-01

Background Major disadvantages of antibiotic bone cements include limited drug release and reduced strength resulting from the addition of high doses of antibiotics. Bacterial cellulose, a three-dimensional hydrophilic mesh, may retain antibiotics and release them gradually. We hypothesized that the addition of cellulose to antibiotic bone cement would improve mechanical strength and antibiotic release. Questions/purposes We therefore examined the mechanical strength and antibiotic release of cellulose antibiotic cement. Methods A high dose of antibiotics (5 g per 40 g cement powder) was incorporated into bacterial cellulose and then mixed with bone cement. We compared the compression strength, fracture toughness, fatigue life, and elution kinetics of this formulation with those of plain cement and a traditional antibiotic cement. Results The average values for compression strength, fracture toughness, and fatigue life of the cellulose antibiotic cement were 97%, 97%, and 78% of the values obtained for plain cement, respectively. The corresponding values for the traditional antibiotic cement were 79%, 82%, and 17%, respectively. The cumulative elution over 35 days was 129% greater from the cellulose antibiotic cement than from the traditional antibiotic cement. Conclusions With a high dose of antibiotics, incorporating cellulose into the bone cement prevented compression and fracture fragility, improved fatigue life, and increased antibiotic elution. Clinical Relevance Antibiotic cements containing cellulose may have applications in clinical situations that require high levels of antibiotic release and preservation of the mechanical properties of the cement. PMID:20945120

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parab, Niranjan D.; Roberts, Zane A.; Harr, Michael H.

Fracture of crystals and subsequent frictional heating are associated with formation of hot spots in energetic composites such as polymer bonded explosives (PBXs). Traditional high speed optical imaging methods cannot be used to study the dynamic sub-surface deformation and fracture behavior of such materials due to their opaque nature. In this study, high speed synchrotron X-ray experiments are conducted to visualize the in situ deformation and fracture mechanisms in PBXs manufactured using octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals and hydroxyl-terminated polybutadiene (HTPB) binder. A modified Kolsky bar apparatus was used to apply controlled dynamic compression on the PBX specimens, and a high speedmore » synchrotron X-ray phase contrast imaging (PCI) setup was used to record the in situ deformation and failure in the specimens. The experiments show that synchrotron X-ray PCI provides a sufficient contrast between the HMX crystals and the doped binder, even at ultrafast recording rates. Under dynamic compression, most of the cracking in the crystals was observed to be due to the tensile stress generated by the diametral compression applied from the contacts between the crystals. Tensile stress driven cracking was also observed for some of the crystals due to the transverse deformation of the binder and superior bonding between the crystal and the binder. In conclusion, the obtained results are vital to develop improved understanding and to validate the macroscopic and mesoscopic numerical models for energetic composites so that eventually hot spot formation can be predicted.« less

Multi-scale geophysical study to model the distribution and development of fractures in relation to the knickpoint in the Luquillo Critical Zone Observatory (Puerto Rico)

NASA Astrophysics Data System (ADS)

Comas, X.; Wright, W. J.; Hynek, S. A.; Ntarlagiannis, D.; Terry, N.; Job, M. J.; Fletcher, R. C.; Brantley, S.

2017-12-01

Previous studies in the Rio Icacos watershed in the Luquillo Mountains (Puerto Rico) have shown that regolith materials are rapidly developed from the alteration of quartz diorite bedrock, and create a blanket on top of the bedrock with a thickness that decreases with proximity to the knickpoint. The watershed is also characterized by a system of heterogeneous fractures that likely drive bedrock weathering and the formation of corestones and associated spheroidal fracturing and rindlets. Previous efforts to characterize the spatial distribution of fractures were based on aerial images that did not account for the architecture of the critical zone below the subsurface. In this study we use an array of near-surface geophysical methods at multiple scales to better understand how the spatial distribution and density of fractures varies with topography and proximity to the knickpoint. Large km-scale surveys using ground penetrating radar (GPR), terrain conductivity, and capacitively coupled resistivity, were combined with smaller scale surveys (10-100 m) using electrical resistivity imaging (ERI), and shallow seismics, and were directly constrained with boreholes from previous studies. Geophysical results were compared to theoretical models of compressive stress as due to gravity and regional compression, and showed consistency at describing increased dilation of fractures with proximity to the knickpoint. This study shows the potential of multidisciplinary approaches to model critical zone processes at multiple scales of measurement and high spatial resolution. The approach can be particularly efficient at large km-scales when applying geophysical methods that allow for rapid data acquisition (i.e. walking pace) at high spatial resolution (i.e. cm scales).

Stronger back muscles reduce the incidence of vertebral fractures: a prospective 10 year follow-up of postmenopausal women.

PubMed

Sinaki, M; Itoi, E; Wahner, H W; Wollan, P; Gelzcer, R; Mullan, B P; Collins, D A; Hodgson, S F

2002-06-01

The long-term protective effect of stronger back muscles on the spine was determined in 50 healthy white postmenopausal women, aged 58-75 years, 8 years after they had completed a 2 year randomized, controlled trial. Twenty-seven subjects had performed progressive, resistive back-strengthening exercises for 2 years and 23 had served as controls. Bone mineral density, spine radiographs, back extensor strength, biochemical marker values, and level of physical activity were obtained for all subjects at baseline, 2 years, and 10 years. Mean back extensor strength (BES) in the back-exercise (BE) group was 39.4 kg at baseline, 66.8 kg at 2 years (after 2 years of prescribed exercises), and 32.9 kg at 10 years (8 years after cessation of the prescribed exercises). Mean BES in the control (C) group was 36.9 kg at baseline, 49.0 kg at 2 years, and 26.9 kg at 10 years. The difference between the two groups was still statistically significant at 10 year follow-up (p = 0.001). The difference in bone mineral density, which was not significant between the two groups at baseline and 2 year follow-up, was significant at 10 year follow-up (p = 0.0004). The incidence of vertebral compression fracture was 14 fractures in 322 vertebral bodies examined (4.3%) in the C group and 6 fractures in 378 vertebral bodies examined (1.6%) in the BE group (chi-square test, p = 0.0290). The relative risk for compression fracture was 2.7 times greater in the C group than in the BE group. To our knowledge, this is the first study reported in the literature demonstrating the long-term effect of strong back muscles on the reduction of vertebral fractures in estrogen-deficient women.

Screw Loosening and Pelvic Canal Narrowing After Lateral Plating of Feline Ilial Fractures With Locking and Nonlocking Plates.

PubMed

Schmierer, Philipp A; Kircher, Patrick R; Hartnack, Sonja; Knell, Sebastian C

2015-10-01

To compare the frequency of complications, including screw loosening and pelvic canal narrowing, associated with dynamic compression plating, locking plating, and double locking plating of ilial fractures in cats. Historical cohort study. The radiographs and medical records of cats with pelvic fractures that were presented between 2004 and 2013 were reviewed. The cases were categorized based on the plate type and number as dynamic compression plate (DCP), single locking plate (LPS) and double locking plates (dLPS). The frequency of screw loosening was compared across categories using a Fisher's exact test. The change in pelvic alignment, described by the change in sacral index (postoperative sacral index-followup sacral index), was compared across plate categories using ANOVA. The frequency of screw loosening for DCP (5/10) was significantly higher than LPS (1/13) and dLPS (0/11) (P = .05, P = .012, respectively). There was no significant difference in the SI change across plate categories. The mean change in sacral index for DCP was -0.11 (95%CI -0.25 to 0.03), for LPS was 0.0007 (95%CI -0.07 to 0.08), and for dLPS was -0.01 (95%CI -0.04 to 0.02). None of the cats showed constipation postoperatively. Screw loosening occurred less often but the change in pelvic canal alignment was not significantly different in ilial fractures repaired with LPS or dLPS compared to ilial fractures repaired with DCP. Locking plating of ilial fractures in cats may offer advantages compared to nonlocking plating. © Copyright 2015 by The American College of Veterinary Surgeons.

Elastic Behavior of a Rubber Layer Bonded between Two Rigid Spheres.

DTIC Science & Technology

1988-05-01

Cracking, Composites, Compressibility, Def ormition, Dilatancy, Elasticity, Elastomers , Failure, Fracture, Particle ’,-1tr1f6rcement, Rubber, Stress...Analysis. 2.AITRACT (Ca~mmi ON VOW...lds It 񔨾Y MtE fIdnt & bp04 bo ambwe - Finite element methods ( FEM ) have been employed to calculate the stresses...deformations set up by compression or extension of the layer, using finite element methods ( FEM ) and not invoking the condition of incompressibility

Does Surgical Stabilization of Lateral Compression-type Pelvic Ring Fractures Decrease Patients' Pain, Reduce Narcotic Use, and Improve Mobilization?

PubMed

Hagen, Jennifer; Castillo, Renan; Dubina, Andrew; Gaski, Greg; Manson, Theodore T; O'Toole, Robert V

2016-06-01

Debate remains over the role of surgical treatment in minimally displaced lateral compression (Young-Burgess, LC, OTA 61-B1/B2) pelvic ring injuries. Lateral compression type 1 (LC1) injuries are defined by an impaction fracture at the sacrum; type 2 (LC2) are defined by a fracture that extends through the posterior iliac wing at the level of the sacroiliac joint. Some believe that operative stabilization of these fractures limits pain and eases mobilization, but to our knowledge there are few controlled studies on the topic. (1) Does operative stabilization of LC1 and LC2 pelvic fractures decrease patients' narcotic use and lower their visual analog scale pain scores? (2) Does stabilization allow patients to mobilize earlier with physical therapy? This retrospective study of LC1 and LC2 fractures evaluated patients treated definitively at one institution from 2007 to 2013. All patients treated surgically, all nonoperative LC2, and all nonoperative LC1 fractures with complete sacral injury were included. In general, LC1 or LC2 fractures with greater than 10 mm of displacement and/or sagittal/axial plane deformity on static radiographs were treated surgically. One hundred fifty-eight patients in the LC1 group (107 [of 697 screened] nonoperative, 51 surgical) and 123 patients in the LC2 group (78 nonoperative, 45 surgical) met inclusion criteria. The surgical and nonoperative groups were matched for fracture type. To account for differences between patients treated surgically and nonoperatively, we used propensity modeling techniques incorporating treatment predictors. Propensity scores demonstrated good overlap and were used as part of multiple variable regression models to account for selection bias between the surgically treated and nonoperative groups. Patient-reported pain scores and narcotic administration were tallied in 24-hour increments during the first 24 hours of hospitalization, at 48 hours after intervention, and in the 24 hours before discharge. Time from intervention to mobilization out of bed was recorded; intervention was defined as the date of definitive surgical intervention or the day the surgeon determined the patient would be treated without surgery. There was no difference in the narcotics distributed to any of the groups with the exception that the patients with surgically treated LC2 fractures used, on average (mean [95% confidence interval]) 40.2 (-72.9 to -7.6) mg morphine less at the 48-hour mark (p = 0.016). In general, there were no differences between the groups' pain scores. The surgically treated patients with LC1 fractures mobilized 1.7 (-3.3 to -0.01) days earlier (p = 0.034) than their nonoperative counterparts. There was no difference in the LC2 cohort in terms of time to mobilization between those treated with and without surgery. There were few differences in pain scores and morphine use between the surgical and nonoperative groups, and the differences observed likely were not clinically important. We found no evidence that surgical stabilization of certain LC1 and LC2 pelvic fractures improves patients' pain, decreases their narcotic use, and improves time to mobilization. A randomized trial of patients with similar fractures and similar degrees initial displacement would help remove some of the confounders present in this study. Level III, therapeutic study.

Vertebral fracture after aircraft ejection during Operation Desert Storm.

PubMed

Osborne, R G; Cook, A A

1997-04-01

During Operation Desert Storm, 21 United States and 2 Italian military personnel were held in Iraq as prisoners of war. Of these, 18 had ejected from fixed-wing, ejection seat-equipped, combat aircraft prior to their capture. Of the 18, 6 (33%) had sustained vertebral fractures; 4 of these were compression fractures. This fracture rate is comparable to that of previously studied groups. Fractures were noted to be at several different vertebral sites and after ejecting from a variety of aircraft. Apart from contusions and abrasions, vertebral fractures were the most common injuries discovered in this repatriated population. None of the vertebral fractures produced recognizable neurological disability. The development of vertebral fractures was neither associated with the use of any particular ejection system or aircraft nor did the development of vertebral fractures appear dependent on the age, height or length of service of the affected personnel. Ejected aircrew with low altitude mission profiles seemed more predisposed to vertebral fracture than those at high altitudes, but with a small sample population, this relationship was not statistically significant (p > 0.25). Reliable data were unavailable on aircrew positioning and preparation time for ejection.

[One-stage operation for pelvis and acetabular fractures combined with Morel-Lavallée injury by internal fixation associated with vacuum sealing drainage].

PubMed

Wei, Dan; Wang, Yue; Yuan, Jiabin; Tang, Xiaoming; Zhang, Bin; Lu, Bing; Tan, Bo

2014-01-01

To investigate the methods and effectiveness of one-stage operation for pelvis and acetabular fractures combined with Morel-Lavallée injury by internal fixation associated with vacuum sealing drainage (VSD). Between June 2008 and October 2012, 15 cases of pelvis and acetabular fractures combined with Morel-Lavallée injury were treated. There were 5 males and 10 females, aged from 18 to 67 years (mean, 36.8 years). Fractures were caused by traffic accident in 11 cases and crashing injury of heavy object in 4 cases. The time from injury to hospitalization was 3 hours to 9 days (mean, 5.4 days). Morel-Lavallée injury located in the above posterior superior iliac spine in 4 cases, greater trochanter in 7 cases, and anterior proximal thigh in 4 cases. In 10 cases complicated by pelvic fracture, there were 1 case of anteroposterior compression type, 3 cases of lateral compression type, 5 cases of vertical shear type, and 1 case of compound injury type; in 5 cases complicated by acetabular fracture, there were 1 case of transverse fracture, 1 case of posterior wall and posterior column fracture, 1 case of transverse acetabulum plus posterior wall fracture, and 2 cases of both columns fracture. Open reduction and internal fixation were used to treat pelvic and acetabular fractures, and VSD to treat Morel-Lavallée injury. When the drainage volume was less than 20 mL/d, interrupted wound suture or free skin grafting was performed. The hospitalization time was 16-31 days (mean, 20.8 days). Thirteen cases were followed up 4-16 months (mean, 7.8 months). The healing time of Morel-Lavallée injury was 16-36 days after operation (mean, 21.3 days). All the wounds had primary healing, and no infection occurred. The X-ray films showed that all fractures healed, with a mean healing time of 13.6 weeks (range, 11-18 weeks). At 6.5 months after operation, according to Majeed function scoring system in 8 cases of pelvic fracture, the results were excellent in 5 cases, good in 2 cases, and fair in 1 case; according to Harris hip scoring in 4 cases of acetabular fracture, the results were excellent in 2 cases, good in 1 case, and fair in 1 case. To pelvis-acetabular fractures combined with Morel-Lavallée injury, internal fixation treatment for fracture and VSD for Morel-Lavallée injury not only can cure merge Morel-Lavallée injury effectively, but also can guarantee the operation timing and incision safty of the pelvis-acetabular fractures.

Application of powder X-ray diffraction in studying the compaction behavior of bulk pharmaceutical powders.

PubMed

Bandyopadhyay, Rebanta; Selbo, Jon; Amidon, Gregory E; Hawley, Michael

2005-11-01

This study investigates the effects of crystal lattice deformation on the powder X-ray diffraction (PXRD) patterns of compressed polycrystalline specimen (compacts/tablets) made from molecular, crystalline powders. The displacement of molecules and the corresponding adjustment of interplanar distances (d-spacings) between diffracting planes of PNU-288034 and PNU-177553, which have crystal habits with a high aspect ratio favoring preferred orientation during tableting, are demonstrated by shifts in the diffracted peak positions. The direction of shift in diffracted peak positions suggests a reduction of interplanar d-spacing in the crystals of PNU-288034 and PNU-177553 following compaction. There is also a general reduction of peak intensities following compression at the different compressive loads. The lattice strain representing the reduction in d-spacing is proportional to the original d-spacing of the uncompressed sample suggesting that, as with systems that obey a simple Hooke's law relationship, the further apart the planes of atoms/molecules within the lattice are, the easier it is for them to approach each other under compressive stresses. For a third model compound comprising more equant-shaped crystals of PNU-141659, the shift in diffracted peak positions are consistent with an expansion of lattice spacing after compression. This apparent anomaly is supported by the PXRD studies of the bulk powder consisting of fractured crystals where also, the shift in peak position suggests expansion of the lattice planes. Thus the crystals of PNU-141659 may be fracturing under the compressive loads used to produce the compacts. Additional studies are underway to relate the PXRD observations with the bulk tableting properties of these model compounds.

Anterior tibial stress fractures treated with anterior tension band plating in high-performance athletes.

PubMed

Cruz, Alexandre Santa; de Hollanda, João Paris Buarque; Duarte, Aires; Hungria Neto, José Soares

2013-06-01

The non-surgical treatment of anterior tibial cortex stress fractures requires long periods of abstention from sports activities and often results in non-union. Many different surgical techniques have already been previously described to treat these fractures, but there is no consensus on the best treatment. We describe the outcome of treatment using anterior tibial tension band plating in three high-performance athletes (4 legs) with anterior tibial cortex stress fractures. Tibial osteosynthesis with a 3.5-mm locking compression plate in the anterolateral aspect of the tibia was performed in all patients diagnosed with anterior tibial stress fracture after September 2010 at Santa Casa Hospital. All of the fractures were consolidated within a period of 3 months after surgery, allowing for an early return to pre-injury levels of competitive sports activity. There were no infection, non-union, malunion or anterior knee pain complications. Anterior tibial tension band plating leads to prompt fracture consolidation and is a good alternative for the treatment of anterior tibial cortex stress fractures. Bone grafts were shown to be unnecessary.

"A" shape plate for open rigid internal fixation of mandible condyle neck fracture.

PubMed

Kozakiewicz, Marcin; Swiniarski, Jacek

2014-09-01

Reduction of the fracture is crucial for proper outcome of the treatment. The stability of reduction is closed connected to the method of its fixation. The topic of condylar fracture osteosynthesis still remains highly controversial and challenging. That is why authors decided to propose novel design of the fixating plate and the example of its application. The aim of this study was to present A-shape plate dedicated to rigid fixation of mandible condyle neck fracture. A-shape condylar plate (ACP) design is prepared of 1.0 mm thick titanium alloy (grade 5) sheet: posterior and anterior bars are reinforced by widening to 2.5 mm and anatomically curved along the compression and traction lines in ramus and condylar neck. Superior three-hole-group has triangular organization and located on the level of condylar head. The inferior extensions of the bars are equipped in three holes located at each of lower tails. Connecting bar (2.0 mm wide) connects the first hole of each lower tails closing upper part of ACP in triangular shape. The connecting bar runs along compression line of condylar neck. Holes in ACP has 2.0 mm diameter for locking or normal screws. Height of ACP is 31 mm. The proposed new type of plate was compared by finite element analysis (FEA) to nowadays manufactured 9-hole trapezoid plate as the most similar device. ACP design was evaluated by finite element analysis (FEA) and later applied in patient affected with high condylar neck fracture complicated by fracture of coronoid process. FEA revealed high strength of ACP and more stabile fixation than trapezoid plate. The result was caused by multipoint fixation at three regions of the plate and reinforced bars supported by semi-horizontal connecting bar. Clinical application of ACP was as versatile as makes possible to simultaneous fixation of high condylar neck and coronoid process fracture. Application of proposed A-shape condylar plate would be possible in all levels of neck fractures and can be use for stabilization additionally existed coronoid process fracture. Copyright © 2013 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Effect of core ceramic grinding on fracture behaviour of bilayered zirconia veneering ceramic systems under two loading schemes.

PubMed

Jian, Yu-Tao; Tang, Tian-Yu; Swain, Michael V; Wang, Xiao-Dong; Zhao, Ke

2016-12-01

The aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes. Interfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis and one-way ANOVA at a significance level of 0.05. As grit size of the diamond disc increased, zirconia surface roughness decreased (p<0.001). Thermal veneering treatment reversed the transformation of monoclinic phase observed after initial grinding. No difference in initial (p=0.519 for subgroups Ac-Dc) and final fracture strength (p=0.699 for subgroups Ac-Dc; p=0.328 for subgroups At-Dt) was found among the four groups for both loading schemes. While coarse grinding slightly increased final fracture strength reliability (m) for subgroups Ac-Dc. Two different modes of fracture were observed according to which material was on the bottom surface. Components of the liner porcelain remained on the zirconia surface after fracture for all groups. Technician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its application on rough zirconia cores may be preferred to enhance bond strength. Copyright © 2016. Published by Elsevier Ltd.

Fracture propagation in Indiana Limestone interpreted via linear softening cohesive fracture model

NASA Astrophysics Data System (ADS)

Rinehart, Alex J.; Bishop, Joseph E.; Dewers, Thomas

2015-04-01

We examine the use of a linear softening cohesive fracture model (LCFM) to predict single-trace fracture growth in short-rod (SR) and notched 3-point-bend (N3PB) test configurations in Indiana Limestone. The broad goal of this work is to (a) understand the underlying assumptions of LCFM and (b) use experimental similarities and deviations from the LCFM to understand the role of loading paths of tensile fracture propagation. Cohesive fracture models are being applied in prediction of structural and subsurface fracture propagation in geomaterials. They lump the inelastic processes occurring during fracture propagation into a thin zone between elastic subdomains. LCFM assumes that the cohesive zone initially deforms elastically to a maximum tensile stress (σmax) and then softens linearly from the crack opening width at σmax to zero stress at a critical crack opening width w1. Using commercial finite element software, we developed LCFMs for the SR and N3PB configurations. After fixing σmax with results from cylinder splitting tests and finding an initial Young's modulus (E) with unconfined compressive strength tests, we manually calibrate E and w1 in the SR model against an envelope of experimental data. We apply the calibrated LCFM parameters in the N3PB geometry and compare the model against an envelope of N3PB experiments. For accurate simulation of fracture propagation, simulated off-crack stresses are high enough to require inclusion of damage. Different elastic moduli are needed in tension and compression. We hypothesize that the timing and location of shear versus extensional micromechanical failures control the qualitative macroscopic force-versus-displacement response in different tests. For accurate prediction, the LCFM requires a constant style of failure, which the SR configuration maintains until very late in deformation. The N3PB configuration does not maintain this constancy. To be broadly applicable between geometries and failure styles, the LCFM would require additional physics, possibly including elastoplastic damage in the bulk material and more complicated cohesive softening models.

A Biomechanical Study of Posteromedial Tibial Plateau Fracture Stability: Do They All Require Fixation?

PubMed

Cuéllar, Vanessa G; Martinez, Danny; Immerman, Igor; Oh, Cheongeun; Walker, Peter S; Egol, Kenneth A

2015-07-01

Although the posteromedial fragment in tibial plateau fractures is often considered unstable, biomechanical evidence supporting this view is lacking. We aimed to evaluate the stability of the fragment in a cadaver model. Our hypothesis was that under the expected small axial force during rehabilitation and the combined effects of this force with shear force, internal rotation torque, and varus moment, the most common posteromedial tibial fragment morphology could maintain stability in early flexion. Axial compression force alone or combined with posterior shear, internal rotation torque, or varus moment was applied to the femurs of 5 fresh cadaveric knees. A Tekscan pressure mapping system was used to measure pressure and contact area between the femoral condyles, meniscus, and tibial plateau. A Microscribe 3D digitizer was used to define the 3-dimensional positions of the femur and tibia. A 10-mm and then a 20-mm osteotomy was created with a saw at an angle of 30 degrees in the axial plane with respect to the tangent of the posterior tibial plateau and 75 degrees in the sagittal plane, representing a typical posteromedial fracture fragment. At each flexion angle (15, 30, 60, 90, and 120 degrees) and loading condition (axial compression only, compression with shear force, torque, and varus moment), distal displacement of the medial femoral condyle and the tibial fracture fragments was determined. For the 10-mm fragment, medial femoral condyle displacement was little affected up to approximately 30-degree flexion, after which it increased. For the 20-mm fragment, there was progressive medial femoral condyle displacement with increasing flexion from baseline. However, for the 10- and 20-mm fragments themselves, displacements were noted at every flexion angle, starting at 1.7 mm inferior displacement with 15 degrees of flexion and internal rotation torque and up to 10.2 mm displacement with 90 degrees of flexion and varus bending moment. In this cadaveric model of a posteromedial tibial plateau fracture, both fracture fragments studied displaced with knee flexion, even at low flexion angles. Although such fragments may initially seem nondisplaced after injury, posteromedial fragments similar to these tested are likely to displace during knee range of motion exercises in non-weight-bearing conditions.

Polymethylmethacrylate distribution is associated with recompression after vertebroplasty or kyphoplasty for osteoporotic vertebral compression fractures: A retrospective study.

PubMed

Hou, Yu; Yao, Qi; Zhang, Genai; Ding, Lixiang; Huang, Hui

2018-01-01

Osteoporotic vertebral compression fracture, always accompanied with pain and height loss of vertebral body, has a significant negative impact on life quality of patients. Vertebroplasty or kyphoplasty is minimal invasive techniques to reconstruct the vertebral height and prevent further collapse of the fractured vertebrae by injecting polymethylmethacrylate into vertebral body. However, recompression of polymethylmethacrylate augmented vertebrae with significant vertebral height loss and aggressive local kyphotic was observed frequently after VP or KP. The purpose of this study was to investigate the effect of polymethylmethacrylate distribution on recompression of the vertebral body after vertebroplasty or kyphoplasty surgery for osteoporotic vertebral compression fracture. A total of 281 patients who were diagnosed with vertebral compression fracture (T5-L5) from June 2014 to June 2016 and underwent vertebroplasty or kyphoplasty by polymethylmethacrylate were retrospectively analyzed. The X-ray films at 1 day and 12 months after surgery were compared to evaluate the recompression of operated vertebral body. Patients were divided into those without recompression (non-recompression group) and those with recompression (recompression group). Polymethylmethacrylate distribution pattern, including location and relationship to endplates, was compared between the two groups by lateral X-ray film. Multivariate logistic regression analysis was performed to assess the potential risk factors associated with polymethylmethacrylate distribution for recompression. One hundred and six (37.7%) patients experienced recompression after surgery during the follow-up period. The polymethylmethacrylate distributed in the middle of vertebral body showed significant differences between two groups. In non-recompression group, the polymethylmethacrylate in the middle portion of vertebral body were closer to endplates than that in the recompression group (upper: t = 31.41, p<0.001; lower: t = 12.19, p<0.001). The higher percentage of the height of polymethylmethacrylate in the middle portion of vertebral body indicates the lower risk of recompression (odds ratio [OR]<0.01, p<0.001). The recompression group and non-recompression group showed significant difference in "contacted" polymethylmethacrylate distribution pattern (polymethylmethacrylate contacted to the both upper/lower endplates) (χ2 = 66.23, p<0.001). The vertebra with a "contacted" polymethylmethacrylate distribution pattern has lower risk of recompression (OR = 0.09, p<0.001). Either more polymethylmethacrylate in the middle portion of vertebral body or "contacted" polymethylmethacrylate distribution pattern had a significantly less incidence of recompression. The findings indicated that the control of polymethylmethacrylate distribution during surgery may reduce the risks of recompression after vertebroplasty or kyphoplasty.

Polymethylmethacrylate distribution is associated with recompression after vertebroplasty or kyphoplasty for osteoporotic vertebral compression fractures: A retrospective study

PubMed Central

Yao, Qi; Zhang, Genai; Ding, Lixiang; Huang, Hui

2018-01-01

Background Osteoporotic vertebral compression fracture, always accompanied with pain and height loss of vertebral body, has a significant negative impact on life quality of patients. Vertebroplasty or kyphoplasty is minimal invasive techniques to reconstruct the vertebral height and prevent further collapse of the fractured vertebrae by injecting polymethylmethacrylate into vertebral body. However, recompression of polymethylmethacrylate augmented vertebrae with significant vertebral height loss and aggressive local kyphotic was observed frequently after VP or KP. The purpose of this study was to investigate the effect of polymethylmethacrylate distribution on recompression of the vertebral body after vertebroplasty or kyphoplasty surgery for osteoporotic vertebral compression fracture. Methods A total of 281 patients who were diagnosed with vertebral compression fracture (T5-L5) from June 2014 to June 2016 and underwent vertebroplasty or kyphoplasty by polymethylmethacrylate were retrospectively analyzed. The X-ray films at 1 day and 12 months after surgery were compared to evaluate the recompression of operated vertebral body. Patients were divided into those without recompression (non-recompression group) and those with recompression (recompression group). Polymethylmethacrylate distribution pattern, including location and relationship to endplates, was compared between the two groups by lateral X-ray film. Multivariate logistic regression analysis was performed to assess the potential risk factors associated with polymethylmethacrylate distribution for recompression. Results One hundred and six (37.7%) patients experienced recompression after surgery during the follow-up period. The polymethylmethacrylate distributed in the middle of vertebral body showed significant differences between two groups. In non-recompression group, the polymethylmethacrylate in the middle portion of vertebral body were closer to endplates than that in the recompression group (upper: t = 31.41, p<0.001; lower: t = 12.19, p<0.001). The higher percentage of the height of polymethylmethacrylate in the middle portion of vertebral body indicates the lower risk of recompression (odds ratio [OR]<0.01, p<0.001). The recompression group and non-recompression group showed significant difference in “contacted” polymethylmethacrylate distribution pattern (polymethylmethacrylate contacted to the both upper/lower endplates) (χ2 = 66.23, p<0.001). The vertebra with a “contacted” polymethylmethacrylate distribution pattern has lower risk of recompression (OR = 0.09, p<0.001). Conclusions Either more polymethylmethacrylate in the middle portion of vertebral body or “contacted” polymethylmethacrylate distribution pattern had a significantly less incidence of recompression. The findings indicated that the control of polymethylmethacrylate distribution during surgery may reduce the risks of recompression after vertebroplasty or kyphoplasty. PMID:29856859

Enhancing overall tensile and compressive response of pure Mg using nano-TiB{sub 2} particulates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meenashisundaram, Ganesh Kumar; Seetharaman, Sankaranarayanan; Gupta, Manoj, E-mail: mpegm@nus.edu.sg

2014-08-15

A novel attempt is made to synthesize and study the isolated effects of less than two volume fraction TiB{sub 2} nanoparticulates (60 nm) on pure magnesium. New light weight Mg–TiB{sub 2} nanocomposites with superior mechanical properties compared to pure magnesium are synthesized using disintegrated melt deposition technique followed by hot extrusion. The microstructural characterization studies revealed that the samples exhibited fairly uniform distribution of TiB{sub 2} nanoparticulates with minimal porosity and good interfacial integrity between Mg matrix and TiB{sub 2} particulates. The coefficient of thermal expansion results indicates that the addition of 0.58, 0.97, and 1.98 vol.% TiB{sub 2} nanoparticulatesmore » marginally improves the dimensional stability of pure magnesium. A significant improvement in the room temperature tensile properties of pure magnesium was observed with the addition of less than two volume fraction TiB{sub 2} nanoparticulates. The synthesized Mg 1.98 vol.% TiB{sub 2} nanocomposite revealed the best room temperature tensile properties with a significant increase in the 0.2% tensile yield strength by ∼ 54%, ultimate tensile strength by ∼ 15% and fracture strain by ∼ 79% when compared to pure Mg. The X-ray diffraction studies indicated changes in the basal plane orientation of pure Mg with the addition of nano-TiB{sub 2} particulates. A maximum tensile fracture strain of ∼ 16% is achieved with the addition of 0.97 vol.% TiB{sub 2}. The room temperature compressive properties of the nanocomposites reveal that the addition of 1.98 TiB{sub 2} increases the 0.2% compressive yield strength of Mg by ∼ 47% and ultimate compressive strength by ∼ 10% with a marginal increase in the fracture strain (∼ 11%). Reduction in tensile–compression yield asymmetry was observed for Mg 0.58 and 0.97 vol.% TiB{sub 2} nanocomposites which can be attributed to the weakening of the strong basal texture of pure Mg. - Highlights: • First attempt is made to synthesize and characterize Mg-TiB{sub 2} nanocomposites. • XRD studies indicate nano TiB{sub 2} addition modifies the basal texture of pure Mg. • Maximum tensile fracture strain of ∼ 16 % in Mg 0.97 vol.% TiB{sub 2} nanocomposite. • Hardness values of Mg-TiB{sub 2} composites indicate superior tribological properties.« less

The Effects of Whole-Body Vibration on Health

DTIC Science & Technology

1979-03-01

strains, sciatica, lumbar disc syndrome, and facet syndrome), cardiovascular system (hypertension, coronary artery disease, obstructive syndromes...compression fractures, Schmorl’s nodes, ankylosing spondylitis, spondylolisthesis, spondylosis , Scheur- man’s disease, supply spondylosis , detached retina

Tensile overpressure compartments on low-angle thrust faults

NASA Astrophysics Data System (ADS)

Sibson, Richard H.

2017-08-01

Hydrothermal extension veins form by hydraulic fracturing under triaxial stress (principal compressive stresses, σ 1 > σ 2 > σ 3) when the pore-fluid pressure, P f, exceeds the least compressive stress by the rock's tensile strength. Such veins form perpendicular to σ 3, their incremental precipitation from hydrothermal fluid often reflected in `crack-seal' textures, demonstrating that the tensile overpressure state, σ 3' = ( σ 3 - P f) < 0, was repeatedly met. Systematic arrays of extension veins develop locally in both sub-metamorphic and metamorphic assemblages defining tensile overpressure compartments where at some time P f > σ 3. In compressional regimes ( σ v = σ 3), subhorizontal extension veins may develop over vertical intervals <1 km or so below low-permeability sealing horizons with tensile strengths 10 < T o < 20 MPa. This is borne out by natural vein arrays. For a low-angle thrust, the vertical interval where the tensile overpressure state obtains may continue down-dip over distances of several kilometres in some instances. The overpressure condition for hydraulic fracturing is comparable to that needed for frictional reshear of a thrust fault lying close to the maximum compression, σ 1. Under these circumstances, especially where the shear zone material has varying competence (tensile strength), affecting the failure mode, dilatant fault-fracture mesh structures may develop throughout a tabular rock volume. Evidence for the existence of fault-fracture meshes around low-angle thrusts comes from exhumed ancient structures and from active structures. In the case of megathrust ruptures along subduction interfaces, force balance analyses, lack of evidence for shear heating, and evidence of total shear stress release during earthquakes suggest the interfaces are extremely weak ( τ < 40 MPa), consistent with weakening by near-lithostatically overpressured fluids. Portions of the subduction interface, especially towards the down-dip termination of the seismogenic megathrust, are prone to episodes of slow-slip, non-volcanic tremor, low-frequency earthquakes, very-low-frequency earthquakes, etc., attributable to the activation of tabular fault-fracture meshes at low σ 3' around the thrust interface. Containment of near-lithostatic overpressures in such settings is precarious, fluid loss curtailing mesh activity.[Figure not available: see fulltext.

Composite materials: Fatigue and fracture. Vol. 3

NASA Technical Reports Server (NTRS)

O'Brien, T. K. (Editor)

1991-01-01

The present volume discusses topics in the fields of matrix cracking and delamination, interlaminar fracture toughness, delamination analysis, strength and impact characteristics, and fatigue and fracture behavior. Attention is given to cooling rate effects in carbon-reinforced PEEK, the effect of porosity on flange-web corner strength, mode II delamination in toughened composites, the combined effect of matrix cracking and free edge delamination, and a 3D stress analysis of plain weave composites. Also discussed are the compression behavior of composites, damage-based notched-strength modeling, fatigue failure processes in aligned carbon-epoxy laminates, and the thermomechanical fatigue of a quasi-isotropic metal-matrix composite.

High performance thermoplastics - A review of neat resin and composite properties

NASA Technical Reports Server (NTRS)

Johnston, Norman J.; Hergenrother, Paul M.

1987-01-01

A review was made of the principal thermoplastics used to fabricate high performance composites. Neat resin tensile and fracture toughness properties, glass transition temperatures (Tg), crystalline melt temperatures (Tm) and approximate processing conditions are presented. Mechanical properties of carbon fiber composites made from many of these thermoplastics are given, including flexural, longitudinal tensile, transverse tensile and in-plane shear properties as well as short beam shear and compressive strengths and interlaminar fracture toughness.

Effects of through-the-thickness stitching on impact and interlaminar fracture properties of textile graphite/epoxy laminates

NASA Technical Reports Server (NTRS)

Sharma, Suresh K.; Sankar, Bhavani V.

1995-01-01

This study investigated the effects of through-the-thickness stitching on impact damage resistance, impact damage tolerance, and mode I and mode II fracture toughness of textile graphite/epoxy laminates. Uniweave resin-transfer-molded 48 ply graphite/epoxy (AS4/3501-6) laminates were stitched with Kevlar and glass yarns of different linear densities and stitch spacings. Delaminations were implanted during processing to simulate impact damage. Sublaminate buckling tests were performed to determine the effects of stitching on the compressive strength. The results showed outstanding improvements of up to 400 percent in the compression strength over the unstitched laminates. In impact and static indentation tests the onset of damage occurred at the same level, but the extent of damage was less in stitched laminates. Mode I fracture toughness of 24 ply Uniweave unidirectional (AS4/3501-6) stitched laminates was measured by conducting double-cantilever-beam tests. The critical strain energy release rate (G(sub Ic)) was found to be up to 30 times higher than the unstitched laminates. Mode II fracture toughness of the Uniweave laminates was measured by performing end-notched-flexure tests. Two new methods to compute the apparent G(sub IIc) are presented. The apparent G(sub IIc) was found to be at least 5-15 times higher for the stitched laminates.

Poor relation between biomechanical and clinical studies for the proximal femoral locking compression plate

PubMed Central

Viberg, Bjarke; Rasmussen, Katrine M V; Overgaard, Søren; Rogmark, Cecilia

2017-01-01

Background and purpose The proximal femur locking compression plate (PF-LCP) is a new concept in the treatment of hip fractures. When releasing new implants onto the market, biomechanical studies are conducted to evaluate performance of the implant. We investigated the relation between biomechanical and clinical studies on PF-LCP. Methods A systematic literature search of relevant biomechanical and clinical studies was conducted in PubMed on December 1, 2015. 7 biomechanical studies and 15 clinical studies were included. Results Even though the biomechanical studies showed equivalent or higher failure loads for femoral neck fracture, the clinical results were far worse, with a 37% complication rate. There were no biomechanical studies on pertrochanteric fractures. Biomechanical studies on subtrochanteric fractures showed that PF-LCP had a lower failure load than with proximal femoral nail, but higher than with angled blade plate. 4 clinical studies had complication rates less than 8% and 9 studies had complication rates between 15% and 53%. Interpretation There was no clear relation between biomechanical and clinical studies. Biomechanical studies are generally inherently different from clinical studies, as they examine the best possible theoretical use of the implant without considering the long-term outcome in a clinical setting. Properly designed clinical studies are mandatory when introducing new implants, and they cannot be replaced by biomechanical studies. PMID:28287002

Sub-micron fracture mechanism in silica-based glass activated by permanent densification from high-strain loading

DOE PAGES

Wereszczak, Andrew A.; Waters, Shirley B.; Parten, Randy J.; ...

2016-04-26

Several silica-based glasses were fractured at high strain energy via drop-weight testing on small specimens. A cylindrical specimen geometry was chosen to promote initially simple, axisymmetric, and uniform compressive loading. The imposed uniaxial compressive strain at impact was sufficiently high to qualitatively cause permanent densification. Produced fragments were collected for postmortem and a fraction of them, for all the silica-based glasses, consistently had distinct sub-micron-sized fractures (~ 300–1000 nm), designated here as “microkernels”, on their surfaces. They would most often appear as a sub-micron pore on the fragment - apparently if the microkernel had popped out as a consequence ofmore » the local crack plane running through it, tensile-strain release, and the associated formation of the fragment it was on. No fractographic evidence was found to show the microkernels were associated with local failure initiation. However, their positioning and habit sometimes suggested they were associated with localized crack branching and that they could have influenced secondary fracturing that occurred during overall crushing and comminution and associated fragment size and shape creation. Furthermore, the size range of these microkernels is much too small to affect structural flexure strength of these glasses for most applications but are of a size and concentration that may affect their ballistic, shock, crush, and comminution responses when permanent densification is concomitantly occurring.« less

Accuracy assessment of the vegetation continuous field tree cover product using 3954 ground plots in the southwestern USA

Treesearch

M. A. White; J. D. Shaw; R. D. Ramsey

2005-01-01

An accuracy assessment of the Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation continuous field (VCF) tree cover product using two independent ground-based tree cover databases was conducted. Ground data included 1176 Forest Inventory and Analysis (FIA) plots for Arizona and 2778 Southwest Regional GAP (SWReGAP) plots for Utah and western Colorado....

WhopGenome: high-speed access to whole-genome variation and sequence data in R.

PubMed

Wittelsbürger, Ulrich; Pfeifer, Bastian; Lercher, Martin J

2015-02-01

The statistical programming language R has become a de facto standard for the analysis of many types of biological data, and is well suited for the rapid development of new algorithms. However, variant call data from population-scale resequencing projects are typically too large to be read and processed efficiently with R's built-in I/O capabilities. WhopGenome can efficiently read whole-genome variation data stored in the widely used variant call format (VCF) file format into several R data types. VCF files can be accessed either on local hard drives or on remote servers. WhopGenome can associate variants with annotations such as those available from the UCSC genome browser, and can accelerate the reading process by filtering loci according to user-defined criteria. WhopGenome can also read other Tabix-indexed files and create indices to allow fast selective access to FASTA-formatted sequence files. The WhopGenome R package is available on CRAN at http://cran.r-project.org/web/packages/WhopGenome/. A Bioconductor package has been submitted. lercher@cs.uni-duesseldorf.de. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Constructing linkage maps in the genomics era with MapDisto 2.0.

PubMed

Heffelfinger, Christopher; Fragoso, Christopher A; Lorieux, Mathias

2017-07-15

Genotyping by sequencing (GBS) generates datasets that are challenging to handle by current genetic mapping software with graphical interface. Geneticists need new user-friendly computer programs that can analyze GBS data on desktop computers. This requires improvements in computation efficiency, both in terms of speed and use of random-access memory (RAM). MapDisto v.2.0 is a user-friendly computer program for construction of genetic linkage maps. It includes several new major features: (i) handling of very large genotyping datasets like the ones generated by GBS; (ii) direct importation and conversion of Variant Call Format (VCF) files; (iii) detection of linkage, i.e. construction of linkage groups in case of segregation distortion; (iv) data imputation on VCF files using a new approach, called LB-Impute. Features i to iv operate through inclusion of new Java modules that are used transparently by MapDisto; (v) QTL detection via a new R/qtl graphical interface. The program is available free of charge at mapdisto.free.fr. mapdisto@gmail.com. Supplementary data are available at Bioinformatics online. © The Author (2017). Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com

GARFIELD-NGS: Genomic vARiants FIltering by dEep Learning moDels in NGS.

PubMed

Ravasio, Viola; Ritelli, Marco; Legati, Andrea; Giacopuzzi, Edoardo

2018-04-14

Exome sequencing approach is extensively used in research and diagnostic laboratories to discover pathological variants and study genetic architecture of human diseases. However, a significant proportion of identified genetic variants are actually false positive calls, and this pose serious challenges for variants interpretation. Here, we propose a new tool named GARFIELD-NGS (Genomic vARiants FIltering by dEep Learning moDels in NGS), which rely on deep learning models to dissect false and true variants in exome sequencing experiments performed with Illumina or ION platforms. GARFIELD-NGS showed strong performances for both SNP and INDEL variants (AUC 0.71 - 0.98) and outperformed established hard filters. The method is robust also at low coverage down to 30X and can be applied on data generated with the recent Illumina two-colour chemistry. GARFIELD-NGS processes standard VCF file and produces a regular VCF output. Thus, it can be easily integrated in existing analysis pipeline, allowing application of different thresholds based on desired level of sensitivity and specificity. GARFIELD-NGS available at https://github.com/gedoardo83/GARFIELD-NGS. edoardo.giacopuzzi@unibs.it. Supplementary data are available at Bioinformatics online.

The threshold strength of laminar ceramics utilizing molar volume changes and porosity

NASA Astrophysics Data System (ADS)

Pontin, Michael Gene

It has been shown that uniformly spaced thin compressive layers within a ceramic body can arrest the propagation of an otherwise catastrophic crack, producing a threshold strength: a strength below which the probability of failure is zero. Previous work has shown that the threshold strength increases with both the magnitude of the compressive stress and the fracture toughness of the thin layer material, and finite element analysis predicts that the threshold strength can be further increased when the elastic modulus of the compressive layer is much smaller than the thicker layer. The current work describes several new approaches to increase the threshold strength of a laminar ceramic system. The initial method utilized a molar volume expansion within the thin layers, produced by the tetragonal-to-monoclinic phase transformation of unstabilized zirconia during cooling, in order to produce large compressive stresses within the thin layers. High threshold strengths were measured for this system, but they remained relatively constant as the zirconia content was increased. It was determined that microcracking produced during the transformation reduced the magnitude of the compressive stresses, but may also have served to reduce the modulus of the thin compressive layer, providing an additional strengthening mechanism. The second approach studied the addition of porosity to reduce the elastic modulus of the thin compressive layers. A new processing method was created and analyzed, in which thick layers of the laminate were fabricated by tape-casting, and then dip-coated into a slurry, containing rice starch, to create thin porous compressive layers upon densification. The effects of porosity on the residual compressive stress, elastic modulus, and fracture toughness of the thin layers were measured and calculated, and it was found that the elastic modulus mismatch between the thin and thick layers produced a large strengthening effect for volume fractions of porosity below a critical level. Specimens with greater volume fractions of porosity exhibited complete crack arrest, typically followed by non-catastrophic failure, as cracks initiating in adjacent thick layers coalesced by cracking or delamination along the thin porous layers.

On the use of a split Hopkinson pressure bar in structural geology: High strain rate deformation of Seeberger sandstone and Carrara marble under uniaxial compression

NASA Astrophysics Data System (ADS)

Zwiessler, Ruprecht; Kenkmann, Thomas; Poelchau, Michael H.; Nau, Siegfried; Hess, Sebastian

2017-04-01

There is increasing evidence that seismogenic fractures can propagate faster than the shear wave velocity of the surrounding rocks. Strain rates within the tip region of such super-shear earthquake ruptures can reach deformation conditions similar to impact processes, resulting in rock pulverization. The physical response of brittle rocks at high strain rates changes dramatically with respect to quasi-static conditions. Rocks become stiffer and their strength increases. A measure for the dynamic behavior of a rock and its strain dependency is the dynamic increase factor (DIF) which is the ratio of the dynamic compressive strength to the quasi-static uniaxial compressive strength. To investigate deformation in the high strain rate regime experimentally, we introduce the split Hopkinson pressure bar technology to the structural geology community, a method that is frequently used by rock and impact engineers. We measure the stress-strain response of homogeneous, fine-grained Seeberger sandstone and Carrara marble in uniaxial compression at strain rates ranging from 10+1 to 10+2 s-1 with respect to tangent modulus and dynamic uniaxial compressive strength. We present full stress-strain response curves of Seeberger sandstone and Carrara marble at high strain rates and an evaluation method to determine representative rates of deformation. Results indicate a rate-dependent elastic behavior of Carrara marble where an average increase of ∼18% could be observed at high strain rates of about 100 s-1. DIF reaches a factor of 2.2-2.4. Seeberger sandstone does not have a rate-dependent linear stress-strain response at high strain rates. Its DIF was found to be about 1.6-1.7 at rates of 100 s-1. The onset of dynamic behavior is accompanied with changes in the fracture pattern from single to multiple fractures to pervasive pulverization for increasing rates of deformation. Seismogenic shear zones and their associated fragment-size spectra should be carefully revisited in the light of dynamic deformation.

[Advanced bone graft combined with locking compression plate for the treatment of middle and distal tibia nonunion].

PubMed

Zhao, Xue; Wang, Pan-feng; Zhang, Yun-tong; Zhang, Chun-cai; Xu, Shuo-gui; Zhang, Xin

2014-12-01

To explore methods of treating middle and distal tibia nonunion with the treatment of advanced bone graft combined with locking compression plate. From January 2011 to December 2012, 12 patients with middle and distal tibia nonunion were treated with advanced bone graft combined with locking compression plate. Among patients, there were 8 males and 4 females aged from 20 to 69 with an average of 47 years old. The time from first injuries to bone nonunion was from 9 months to 5 years, avergaed 19 months. Four cases were treated with external fixation, 6 cases were treated with plate fixation, 2 cases of 12 patients occurred broken of plate and nail. Eleven patients were non-infective bone nonunion and 1 patient was infective bone nonunion. Preoperative X-ray and CT showed all patients had sequestration and formation of ossified bone with different degrees. Operative time, blood loss, wound healing were observed, fracture healing time was evaluated by postoperative X-ray. Johner-Wruhs scoring standards was used to evaluate ankle joint function after operation at 10 months. Operative time ranged from 90 to 185 min with an average of (125.00±20.15) min; blood loss ranged from 225 to 750 ml with an average of (415.00±120.00) ml. All patients were followed up from 10 months to 2.5 years with an average of 1.5 years. Postoperative X-ray showed bone union was formed around fracture after operation at 4 months in all patients, 3 cases obtained bone healing within 6 months after operation, 9 cases obtained from 8 to 12 months. No infection, injury of nerve and vessles, and broken of plate and nail were ocurred. According to Johner-Wruhs scoring at 10 months after operation, 10 cases obtained excellent results, 1 good and 1 moderate. Advanced bone graft combined with locking compression plate, which can build fracture multi-point supporting based on full compression of bone nonunion to get effective fixation, is an effective method in treating middle and distal tibia nonunion.

Minimally invasive plate osteosynthesis with locking compression plate for distal diametaphyseal tibia fracture.

PubMed

Shrestha, D; Acharya, B M; Shrestha, P M

2011-01-01

Distal diametaphyseal tibia fracture though requires operative treatment is difficult to manage. Conventional osteosynthesis is not suitable because distal tibia is subcutaneous bone with poor vascularity. Closed reduction and minimally invasive plate osteosynthesis (MIPO) with locking compression plate (LCP) has emerged as an alternative treatment option because it respects biology of distal tibia and fracture hematoma and also provides biomechanicaly stable construct. To find out suitability of MIPO with LCP for distal diametaphyseal tibia fracture including union time and complicatios and compare wih other available management options in literature. Twenty patients with closed distal diametaphyseal tibia fracture with or without intra articular extension (AO classification: 12 type 43A1, 4 type 43A2, 2 type 43A3 and 2 type 43B1) treated with MIPO with LCP were prospectively followed for average duration of 18.45 months (range 5-30 months). Average duration of injury-hospital and injury-surgery interval was 12.8 hrs (range 2-44 hrs) and 4.45 days (range 1-10 days) respectively. All fractures got united with an average duration of 18.5 weeks (range14-28weeks) except one case of delayed union which was managed with percutaneous bone marrow injection. Two patients had union with valgus angulation less than 5 degees but no nonunion was found. There were two superficial and one deep post operative wound infection. All infections healed with extended period of intravenous antibiotics besides repeated debridemet for deep infection. Implants were removed in eight patients among whom six (30%) had malleolar skin irritation and pain due to prominent hardware. The present case series shows that MIPO with LCP is an effective treatment method in terms of union time and complications rate for distal diametaphyseal tibia fracture. Malleolar skin irritation is common problem because of prominent hardware.

Evaluation on Compressive Characteristics of Medical Stents Applied by Mesh Structures

NASA Astrophysics Data System (ADS)

Hirayama, Kazuki; He, Jianmei

2017-11-01

There are concerns about strength reduction and fatigue fracture due to stress concentration in currently used medical stents. To address these problems, meshed stents applied by mesh structures were interested for achieving long life and high strength perfromance of medical stents. The purpose of this study is to design basic mesh shapes to obatin three dimensional (3D) meshed stent models for mechanical property evaluation. The influence of introduced design variables on compressive characteristics of meshed stent models are evaluated through finite element analysis using ANSYS Workbench code. From the analytical results, the compressive stiffness are changed periodically with compressive directions, average results need to be introduced as the mean value of compressive stiffness of meshed stents. Secondly, compressive flexibility of meshed stents can be improved by increasing the angle proportional to the arm length of the mesh basic shape. By increasing the number of basic mesh shapes arranged in stent’s circumferential direction, compressive rigidity of meshed stent tends to be increased. Finaly reducing the mesh line width is found effective to improve compressive flexibility of meshed stents.

Lateral Compression-I Pelvic Ring Injury: Not Benign to the Developing Fetus.

PubMed

Weinlein, John C; Mashru, Rakesh P; Perez, Edward A; Johnson, Sara E

2018-02-01

To determine whether certain patterns of pelvic ring injury are associated with more frequent intrauterine fetal demise (IUFD). Retrospective review. Level 1 trauma center. Of 44 pregnant patients with pelvic and/or acetabular fractures, 40 had complete records that allowed determination of fetal viability. χ2 tests were used for categorical variables (Fisher exact tests when expected cell counts were fewer than 5), and t tests were used for continuous variables. Fetal or maternal death. Sixteen patients had isolated acetabular fractures, 25 had isolated pelvic ring injuries, and 3 had acetabular fractures with concomitant pelvic ring injuries. Maternal and fetal mortality were 2% and 40%, respectively. No patients with isolated acetabular fractures experienced IUFD, compared with 68% (15/22) of those with isolated pelvic ring injuries (P < 0.0001). Eight (53%) of 15 IUFDs were associated with lateral compression (LC)-I pelvic ring injuries (Orthopaedic Trauma Association/Arbeitsgemeinschaft für Osteosynthesefragen 61-B2). Of the 13 LC-I pelvic ring injuries, 8 (62%) resulted in IUFD. Pelvic ring stability, Young-Burgess classification, and operative treatment were not associated with IUFD. Maternal Glasgow Coma Scale (average 13.2) and Injury Severity Score (average 18.2) at admission were predictive of IUFD. The most frequent pelvic fractures in gravid trauma patients are LC-I. Although the rate of maternal mortality was low, the risk of IUFD was quite high (40%). LC-I pelvic ring injuries often had catastrophic outcomes, with IUFD in 62% of cases. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Constitutive Relations of Randomly Oriented Steel Fiber Reinforced Concrete under Multiaxial Compressive Loadings,

DTIC Science & Technology

1981-12-01

This was done to observe the effect of specimen age on strength after the curing period of 7 days in the humidity room and the remaining time in air in... fatigue resistance. Although the compressive strength is not much improved, the brittle behavior that would occur in plain concrete after peak strength...such as fracture toughness, fatigue resistance, impact resistance and flexural strength (82). The idea of fiber reinforcement applications is not new

Compression Strength of Sulfur Concrete Subjected to Extreme Cold

NASA Technical Reports Server (NTRS)

Grugel, Richard N.

2008-01-01

Sulfur concrete cubes were cycled between liquid nitrogen and room temperature to simulate extreme exposure conditions. Subsequent compression testing showed the strength of cycled samples to be roughly five times less than those non-cycled. Fracture surface examination showed de-bonding of the sulfur from the aggregate material in the cycled samples but not in those non-cycled. The large discrepancy found, between the samples is attributed to the relative thermal properties of the materials constituting the concrete.

Fluid Production Induced Stress Analysis Surrounding an Elliptic Fracture

NASA Astrophysics Data System (ADS)

Pandit, Harshad Rajendra

Hydraulic fracturing is an effective technique used in well stimulation to increase petroleum well production. A combination of multi-stage hydraulic fracturing and horizontal drilling has led to the recent boom in shale gas production which has changed the energy landscape of North America. During the fracking process, highly pressurized mixture of water and proppants (sand and chemicals) is injected into to a crack, which fractures the surrounding rock structure and proppants help in keeping the fracture open. Over a longer period, however, these fractures tend to close due to the difference between the compressive stress exerted by the reservoir on the fracture and the fluid pressure inside the fracture. During production, fluid pressure inside the fracture is reduced further which can accelerate the closure of a fracture. In this thesis, we study the stress distribution around a hydraulic fracture caused by fluid production. It is shown that fluid flow can induce a very high hoop stress near the fracture tip. As the pressure gradient increases stress concentration increases. If a fracture is very thin, the flow induced stress along the fracture decreases, but the stress concentration at the fracture tip increases and become unbounded for an infinitely thin fracture. The result from the present study can be used for studying the fracture closure problem, and ultimately this in turn can lead to the development of better proppants so that prolific well production can be sustained for a long period of time.

Simultaneous Application of Fibrous Piezoresistive Sensors for Compression and Traction Detection in Glass Laminate Composites

PubMed Central

Nauman, Saad; Cristian, Irina; Koncar, Vladan

2011-01-01

This article describes further development of a novel Non Destructive Evaluation (NDE) approach described in one of our previous papers. Here these sensors have been used for the first time as a Piecewise Continuous System (PCS), which means that they are not only capable of following the deformation pattern but can also detect distinctive fracture events. In order to characterize the simultaneous compression and traction response of these sensors, multilayer glass laminate composite samples were prepared for 3-point bending tests. The laminate sample consisted of five layers of plain woven glass fabrics placed one over another. The sensors were placed at two strategic locations during the lay-up process so as to follow traction and compression separately. The reinforcements were then impregnated in epoxy resin and later subjected to 3-point bending tests. An appropriate data treatment and recording device has also been developed and used for simultaneous data acquisition from the two sensors. The results obtained, under standard testing conditions have shown that our textile fibrous sensors can not only be used for simultaneous detection of compression and traction in composite parts for on-line structural health monitoring but their sensitivity and carefully chosen location inside the composite ensures that each fracture event is indicated in real time by the output signal of the sensor. PMID:22163707

Simultaneous application of fibrous piezoresistive sensors for compression and traction detection in glass laminate composites.

PubMed

Nauman, Saad; Cristian, Irina; Koncar, Vladan

2011-01-01

This article describes further development of a novel Non Destructive Evaluation (NDE) approach described in one of our previous papers. Here these sensors have been used for the first time as a Piecewise Continuous System (PCS), which means that they are not only capable of following the deformation pattern but can also detect distinctive fracture events. In order to characterize the simultaneous compression and traction response of these sensors, multilayer glass laminate composite samples were prepared for 3-point bending tests. The laminate sample consisted of five layers of plain woven glass fabrics placed one over another. The sensors were placed at two strategic locations during the lay-up process so as to follow traction and compression separately. The reinforcements were then impregnated in epoxy resin and later subjected to 3-point bending tests. An appropriate data treatment and recording device has also been developed and used for simultaneous data acquisition from the two sensors. The results obtained, under standard testing conditions have shown that our textile fibrous sensors can not only be used for simultaneous detection of compression and traction in composite parts for on-line structural health monitoring but their sensitivity and carefully chosen location inside the composite ensures that each fracture event is indicated in real time by the output signal of the sensor.

Synthesis and mechanical properties of double cross-linked gelatin-graphene oxide hydrogels.

PubMed

Piao, Yongzhe; Chen, Biqiong

2017-08-01

Gelatin is an interesting biological macromolecule for biomedical applications. Here, double cross-linked gelatin nanocomposite hydrogels with incorporation of graphene oxide (GO) were synthesized in one pot using glutaraldehyde (GTA) and GTA-grafted GO as double chemical cross-linkers. The nanocomposite hydrogels, in contrast to the neat gelatin hydrogel, exhibited significant increases in mechanical properties by up to 288% in compressive strength, 195% in compressive modulus, 267% in compressive fracture energy and 160% shear storage modulus with the optimal GO concentration. Fourier transform infrared spectroscopy, scanning electron microscopy and swelling tests were implemented to characterize the nanocomposite hydrogels. Copyright © 2017 Elsevier B.V. All rights reserved.

Toughening of PMR composites by semi-interpenetrating networks

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Srinivansan, K.

1991-01-01

Polymerization of monomer reactants (PMR-15) type polyimide and RP46 prepregs were drum wound using IM-7 fibers. Prepregging and processing conditions were optimized to yield good quality laminates with fiber volume fractions of 60 percent (+/- 2 percent). Samples were fabricated and tested to determine comprehensive engineering properties of both systems. These included 0 deg flexure, short beam shear, transverse flexure and tension, 0 deg tension and compression, intralaminar shear, short block compression, mode 1 and 2 fracture toughness, and compression after impact properties. Semi-2-IPN (interpenetrating polymer networks) toughened PMR-15 and RP46 laminates were also fabricated and tested for the same properties.

Assessment of intra-granular and extra-granular fracture in the development of tablet tensile strength.

PubMed

Mitra, Biplob; Hilden, Jon; Litster, James D

2018-05-24

When a tablet is compacted from deformable granules and then broken, the fracture plane may cleave granules in two (intra-granular fracture) or separate neighboring granules (extra-granular fracture). In this study, a novel method was developed to quantify the extent of intra- versus extra-granular fracture by compacting tablets from multi-colored ideal granules and evaluating fracture surfaces. The proportions of intra-granular and extra-granular fracture were quantified and modeled in light of a new metric, the deformation potential, Δ, reflecting the solid fraction increase as an initial granule bed is compressed into a final tablet. Results show that a measurable tablet strength is achieved at Δ > 0.18, but intra-granular fracture is not observed until Δ > 0.21. At very large Δ, tablets experience almost exclusively intra-granular fracture, yet the tablet tensile strength is considerably lower than that of a tablet compacted from raw powders versus pre-compacted granules. Thus, secondary compaction of granules appears to weaken the granule matrix, leading to reduced tablet tensile strength even in the presence of strong extra-granular bonding. Copyright © 2018. Published by Elsevier Inc.

Strength, Fracture Toughness, Fatigue, and Standardization Issues of Free-standing Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Zhu, Dong-Ming; Miller, Robert A.

2003-01-01

Strength, fracture toughness and fatigue behavior of free-standing thick thermal barrier coatings of plasma-sprayed ZrO2-8wt % Y2O3 were determined at ambient and elevated temperatures in an attempt to establish a database for design. Strength, in conjunction with deformation (stress-strain behavior), was evaluated in tension (uniaxial and trans-thickness), compression, and uniaxial and biaxial flexure; fracture toughness was determined in various load conditions including mode I, mode II, and mixed modes I and II; fatigue or slow crack growth behavior was estimated in cyclic tension and dynamic flexure loading. Effect of sintering was quantified through approaches using strength, fracture toughness, and modulus (constitutive relations) measurements. Standardization issues on test methodology also was presented with a special regard to material's unique constitutive relations.

The role of physical activity in bone health: a new hypothesis to reduce risk of vertebral fracture.

PubMed

Sinaki, Mehrsheed

2007-08-01

Locomotion has always been a major criterion for human survival. Thus, it is no surprise that science supports the dependence of bone health on weight-bearing physical activities. The effect of physical activity on bone is site-specific. Determining how to perform osteogenic exercises, especially in individuals who have osteopenia or osteoporosis, without exceeding the biomechanical competence of bone always poses a dilemma and must occur under medical advice. This article presents the hypothesis that back exercises performed in a prone position, rather than a vertical position, may have a greater effect on decreasing the risk for vertebral fractures without resulting in compression fracture. The risk for vertebral fractures can be reduced through improvement in the horizontal trabecular connection of vertebral bodies.

Femoral fracture repair using a locking plate technique in an adult captive polar bear (Ursus maritimus).

PubMed

Zimmerman, Dawn M; Dew, Terry; Douglass, Michael; Perez, Edward

2010-02-01

To report successful femoral fracture repair in a polar bear. Case report. Female polar bear (Ursus maritimus) 5 years and approximately 250 kg. A closed, complete, comminuted fracture of the distal midshaft femur was successfully reduced and stabilized using a compression plating technique with 2 specialized human femur plates offering axial, rotational, and bending support, and allowing the bone to share loads with the implant. Postoperative radiographs were obtained at 11.5 weeks, 11 months, and 24 months. Bone healing characterized by marked periosteal reaction was evident at 11 months with extensive remodeling evident at 24 months. No complications were noted. Distal mid shaft femoral fracture was reduced, stabilized, and healed in an adult polar bear with a locking plate technique using 2 plates. Previously, femoral fractures in polar bears were considered irreparable. Use of 2 plates applied with a locking plate technique can result in successful fracture repair despite large body weight and inability to restrict postoperative activity.

Fractography of human intact long bone by bending.

PubMed

Kimura, T; Ogawa, K; Kamiya, M

1977-05-27

Human intact tibiae were tested using the static bending method to learn about the relationship between the fracture surface and the failure mode. The bending test was applied to test pieces and to whole bones. The fracture surface was observed by scanning electron microscopy. The bone fracture is closely related to the architecture of the bone substance, especially to the direction of the Haversian canals and the lamellae. The failure mode and the sequence of the break line of the bone can be found out by the observation on the fracture surface. Hardly any crushing effects caused by the compressive force is seen. The mechanical properties of the fractured bone can be estimated to some extend by considering the direction of the break line and the failure mode. The strength calculated by the simple beam formula for elastic materials can not be obtained directly because of the plastic deformation of the bone. The results of the tensile test may be applied to the fracture using the static bending moment.

Management of comminuted proximal ulna fracture-dislocations using a multiplanar locking intramedullary nail.

PubMed

Edwards, Scott G; Argintar, Evan; Lamb, Joshua

2011-06-01

Intramedullary nails have been used for the fixation of olecranon fractures in an attempt to reduce the soft tissue irritation and resulting need for hardware removal seen with plating and tension banding. Further benefits include preservation of vascular supply, and increase stability and improved compression over some alternative techniques. Most intramedullary nails have been limited to simple olecranon fractures or osteotomies. One novel multiplanar, locking intramedullary nail, however, is indicated to stabilize all fracture patterns of the proximal ulna, including the coronoid. This particular locking nail has screws that radiate in multiple planes and form a fixed-angle lattice throughout the bone. The nail also has fixed-angle screws dedicated to the 3 parts of the coronoid: process tip, medial facet, and medial wall. This allows the nail to secure multiple fragments regardless of the fracture pattern's extent of instability. The objective of this article is to illustrate the recommended steps in reducing and stabilizing a comminuted proximal ulna fracture-dislocation using this multiplanar locking intramedullary nail.

Short-fibre reinforcement of calcium phosphate bone cement.

PubMed

Buchanan, F; Gallagher, L; Jack, V; Dunne, N

2007-02-01

Calcium phosphate cement (CPC) sets to form hydroxyapatite, a major component of mineral bone, and is gaining increasing interest in bone repair applications. However, concerns regarding its brittleness and tendency to fragment have limited its widespread use. In the present study, short-fibre reinforcement of an apatitic calcium phosphate has been investigated to improve the fracture behaviour. The fibres used were polypropylene (PP) fibres, 50 microm in diameter and reduced in length by cryogenic grinding. The compressive strength and fracture behaviour were examined. Fibre addition of up to 10 wt % had a significant effect on composite properties, with the energy absorbed during failure being significantly increased, although this tended to be accompanied with a slight drop in compressive strength. The fibre reinforcement mechanisms appeared to be crack bridging and fibre pull-out. The setting time of the CPC with fibre reinforcement was also investigated and was found to increase with fibre volume fraction.

Late diagnosis of multiple myeloma: a case report

NASA Astrophysics Data System (ADS)

Syahreza, A.; Gatot, D.; Mardia, A. I.

2018-03-01

Multiple myeloma is a challenging hematologic case to handle. Sometimes the disease is diagnosed too late for the patient and doctor. Therefore, careful approaches are needed to manage the patient. A 66-year-old mansuffersfrom low back pain since one year before he came to the hospital. He was diagnosed multiple compression fractures by orthopedic and had undergone two surgeries in one year. Punched out lesions werein skull radiology and lumbar compression in lumbar MRI. After further investigation, plasmacytoma and M protein in urine electrophoresis were founded. Significant improvement found after bortezomib and dexamethasone were given.Diagnosis and management of multiple myeloma is a challenge for a doctor. Systematically approach is needed for a patient with a recurrent fracture. Even a novel therapies are not widely available in our country.We reported a late diagnosis of multiple myeloma and had a significant improvement after bortezomib and dexamethasone therapy.

Deformation behavior of human dentin in liquid nitrogen: a diametral compression test.

PubMed

Zaytsev, Dmitry; Panfilov, Peter

2014-09-01

Contribution of the collagen fibers into the plasticity of human dentin is considered. Mechanical testing of dentin at low temperature allows excluding the plastic response of its organic matrix. Therefore, deformation and fracture behavior of the dentin samples under diametral compression at room temperature and liquid nitrogen temperature are compared. At 77K dentin behaves like almost brittle material: it is deformed exclusively in the elastic regime and it fails due to growth of the sole crack. On the contrary, dentin demonstrates the ductile response at 300K. There are both elastic and plastic contributions in the deformation of dentin samples. Multiple cracking and crack tip blunting precede the failure of samples. Organic phase plays an important role in fracture of dentin: plasticity of the collagen fibers could inhibit the crack growth. Copyright © 2014 Elsevier B.V. All rights reserved.

Mechanical properties of new dental pulp-capping materials.

PubMed

Nielsen, Matthew J; Casey, Jeffery A; VanderWeele, Richard A; Vandewalle, Kraig S

2016-01-01

The mechanical properties of pulp-capping materials may affect their resistance to fracture during placement of a final restorative material or while supporting an overlying restoration over time. The purpose of this study was to compare the compressive strength, flexural strength, and flexural modulus of 2 new pulp-capping materials (TheraCal LC and Biodentine), mineral trioxide aggregate (MTA), and calcium hydroxide over time. Specimens were created in molds and tested to failure in a universal testing machine after 15 minutes, 3 hours, and 24 hours. The MTA specimens did not set at 15 minutes. At all time periods, TheraCal LC had the greatest compressive and flexural strengths. After 3 and 24 hours, Biodentine had the greatest flexural modulus. TheraCal LC had greater early strength to potentially resist fracture during immediate placement of a final restorative material. Biodentine had greater stiffness after 3 hours to potentially provide better support of an overlying restoration under function over time.

Effect of the state of internal boundaries on granite fracture nature under quasi-static compression

NASA Astrophysics Data System (ADS)

Damaskinskaya, E. E.; Panteleev, I. A.; Kadomtsev, A. G.; Naimark, O. B.

2017-05-01

Based on an analysis of the spatial distribution of hypocenters of acoustic emission signal sources and an analysis of the energy distributions of acoustic emission signals, the effect of the liquid phase and a weak electric field on the spatiotemporal nature of granite sample fracture is studied. Experiments on uniaxial compression of granite samples of natural moisture showed that the damage accumulation process is twostage: disperse accumulation of damages is followed by localized accumulation of damages in the formed macrofracture nucleus region. In energy distributions of acoustic emission signals, this transition is accompanied by a change in the distribution shape from exponential to power-law. Granite water saturation qualitatively changes the damage accumulation nature: the process is delocalized until macrofracture with the exponential energy distribution of acoustic emission signals. An exposure to a weak electric field results in a selective change in the damage accumulation nature in the sample volume.

Investigating the weight ratio variation of alginate-hydroxyapatite composites for vertebroplasty method bone filler material

NASA Astrophysics Data System (ADS)

Lestari, Gusti Ruri; Yuwono, Akhmad Herman; Sofyan, Nofrijon; Ramahdita, Ghiska

2017-02-01

One of the newly developed methods for curing spinal fracture due to osteoporosis is vertebroplasty. The method is basically based on injection of special material directly to the fractured spine in order to commence the formation of new bone. Therefore, appropriate injectable materials are very important to the curing success. In this study, injectable alginate-hydroxyapatite (HA) composites were fabricated varying the weight percentage of alginate upon synthesis procedure. The result of injection capability and compressive tests as well as Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) suggested that bone filler composite containing 60 wt% alginate is the optimum composition obtaining a compressive modulus up to 0.15 MPa, injection capability of more than 85% and morphology with uniform porous and fibrous structure. This injectable composite fabrication process can be used for the development of injectable materials system for vertebroplasty method.

A review of complications associated with vertebroplasty and kyphoplasty as reported to the Food and Drug Administration medical device related web site.

PubMed

Nussbaum, David A; Gailloud, Philippe; Murphy, Kieran

2004-11-01

In 2002, approximately 38,000 vertebroplasties and 16,000 kyphoplasties were performed in the United States. As the use of both modalities for the treatment of vertebral compression fractures has increased, so have questions regarding safety and efficacy. The authors addressed this by reviewing both the current literature and complications data reported to the Food and Drug Administration (FDA) Center for Devices and Radiological Health through the on-line database (http://www.fda.gov/cdrh/maude.html) and through the Office of the Freedom of Information Act at the FDA. Although both procedures are largely safe, the FDA data highlight two main concerns: reactions to the use of acrylic (polymethylmethacrylate) bone cement, including hypotension and, in some cases, death, especially when multiple vertebral levels are treated in one setting; and a possible increased risk with kyphoplasty of pedicle fracture and cord compression.

Long-bone fractures in persons with spinal cord injury.

PubMed

Frotzler, A; Cheikh-Sarraf, B; Pourtehrani, M; Krebs, J; Lippuner, K

2015-09-01

Retrospective data analysis. To document fracture characteristics, management and related complications in individuals with traumatic spinal cord injury (SCI). Rehabilitation centre for SCI individuals. Patients' records were reviewed. Patients with traumatic SCI and extremity fractures that had occurred after SCI were included. Patient characteristics, fractured bone, fracture localisation, severity and management (operative/conservative), and fracture-related complications were extracted. A total of 156 long-bone fractures in 107 SCI patients (34 women and 73 men) were identified. The majority of patients were paraplegics (77.6%) and classified as American Spinal Injury Association Impairment Scale A (86.0%). Only the lower extremities were affected, whereby the femur (60.9% of all fractures) was fractured more frequently than the lower leg (39.1%). A total of 70 patients (65.4%) had one fracture, whereas 37 patients (34.6%) had two or more fractures. Simple or extraarticular fractures were most common (75.0%). Overall, 130 (83.3%) fractures were managed operatively. Approximately half of the femur fractures (48.2%) were treated with locking compression plates. In the lower leg, fractures were mainly managed with external fixation (48.8%). Conservative fracture management was applied in 16.7% of the cases and consisted of braces or a well-padded soft cast. Fracture-associated complications were present in 13.5% of the cases but did not differ significantly between operative (13.1%) and conservative (15.4%) fracture management. SCI was associated with simple or extraarticular fractures of the distal femur and the lower leg. Fractures were mainly managed operatively with a low complication rate.

Frequency of rib and sternum fractures associated with out-of-hospital cardiopulmonary resuscitation is underestimated by conventional chest X-ray.

PubMed

Lederer, Wolfgang; Mair, Dieter; Rabl, Walter; Baubin, Michael

2004-02-01

Fractured ribs and sternum are frequent complications of thoracic compression during CPR in adults. This study was conducted to determine whether findings of plain chest radiography (CXR) correlate with post-mortem findings in patients who underwent cardiopulmonary resuscitation (CPR) after out-of-hospital cardiac arrest. CXR findings and autopsy results of CPR-related chest injuries comprising rib and sternum fractures were compared prospectively in 19 patients. Fractures were diagnosed in nine of 19 patients by means of radiology and in 18 of 19 patients by autopsy (rib fractures in 6/19 versus 17/19, P=0.002; sternum fractures in 5/19 versus in 9/19, P=0.227. The total number of isolated bone fractures detected by CXR was 18 (12 rib and six sternum fractures) and by autopsy 92 (83 rib and nine sternum fractures). The majority of rib fractures was located in the anterior part of the thoracic cage. Sternum fractures predominantly occurred in the lower third. Eight of 19 patients received either thrombolytic or antithrombotic treatment during CPR but no major bleeding complication associated with CPR was detected by autopsy. The findings of this study indicate that fractures associated with CPR are underreported in conventional radiographic investigations. No major bleeding complications related to CPR-associated fractures was detected.

Efficient and robust compositional two-phase reservoir simulation in fractured media

NASA Astrophysics Data System (ADS)

Zidane, A.; Firoozabadi, A.

2015-12-01

Compositional and compressible two-phase flow in fractured media has wide applications including CO2 injection. Accurate simulations are currently based on the discrete fracture approach using the cross-flow equilibrium model. In this approach the fractures and a small part of the matrix blocks are combined to form a grid cell. The major drawback is low computational efficiency. In this work we use the discrete-fracture approach to model the fractures where the fracture entities are described explicitly in the computational domain. We use the concept of cross-flow equilibrium in the fractures (FCFE). This allows using large matrix elements in the neighborhood of the fractures. We solve the fracture transport equations implicitly to overcome the Courant-Freidricks-Levy (CFL) condition in the small fracture elements. Our implicit approach is based on calculation of the derivative of the molar concentration of component i in phase (cαi ) with respect to the total molar concentration (ci ) at constant volume V and temperature T. This contributes to significant speed up of the code. The hybrid mixed finite element method (MFE) is used to solve for the velocity in both the matrix and the fractures coupled with the discontinuous Galerkin (DG) method to solve the species transport equations in the matrix, and a finite volume (FV) discretization in the fractures. In large scale problems the proposed approach is orders of magnitude faster than the existing models.

Impact fragmentation of a brittle metal compact

NASA Astrophysics Data System (ADS)

Tang, Megan; Hooper, Joseph P.

2018-05-01

The fragmentation behavior of a metal powder compact which is ductile in compression but brittle in tension is studied via impact experiments and analytical models. Consolidated metal compacts were prepared via cold-isostatic pressing of <10 μm zinc powder at 380 MPa followed by moderate annealing at 365 °C. The resulting zinc material is ductile and strain-hardening in high-rate uniaxial compression like a traditional metal, but is elastic-brittle in tension with a fracture toughness comparable to a ceramic. Cylindrical samples were launched up to 800 m/s in a gas gun into thin aluminum perforation targets, subjecting the projectile to a complex multiaxial and time-dependent stress state that leads to catastrophic fracture. A soft-catch mechanism using low-density artificial snow was developed to recover the impact debris, and collected fragments were analyzed to determine their size distribution down to 30 μm. Though brittle fracture occurs along original particle boundaries, no power-law fragmentation behavior was observed as is seen in other low-toughness materials. An analytical theory is developed to predict the characteristic fragment size accounting for both the sharp onset of fragmentation and the effect of increasing impact velocity.

Pattern zoology in biaxially pre-stretched elastic bilayers: from wrinkles and creases to fracture-like ridges

NASA Astrophysics Data System (ADS)

Al-Rashed, Rashed; Lopez JiméNez, Francisco; Reis, Pedro

The wrinkling of elastic bilayers under compression has been explored as a method to produce reversible surface topography, with applications ranging from microfluidics to tunable optics. We introduce a new experimental system to study the effects of pre-stretching on the instability patterns that result from the biaxial compression of thin shells bound to an elastic substrate. A pre-stretched substrate is first prepared by pressurizing an initially flat elastomeric disk and bulging it into a nearly hemispherical thick shell. The substrate is then coated with a thin layer of a polymer suspension, which, upon curing, results in a thin shell of nearly constant thickness. Releasing the pre-stretch in the substrate by deflating the system places the outer film in a state of biaxial compression, resulting in a variety of buckling patterns. We explore the parameter space by systematically varying the pre-stretch, the substrate/film stiffness mismatch, and the thickness of the film. This results in a continuous transition between different buckling patterns, from the dimples and wrinkles that are traditionally associated with the buckling of elastic bilayers, to creases and high aspect ratio `fracture-like' ridges, where the pre-stretch plays an essential role.

Biomechanical analysis of four different fixations for the posterolateral shearing tibial plateau fracture.

PubMed

Zhang, Wei; Luo, Cong-Feng; Putnis, Sven; Sun, Hui; Zeng, Zhi-Min; Zeng, Bing-Fang

2012-03-01

The posterolateral shearing tibial plateau fracture is uncommon in the literature, however with the increased usage of computer tomography (CT), the incidence of these fractures is no longer as low as previously thought. Few studies have concentrated on this fracture, least of all using a biomechanical model. The purpose of this study was to compare and analyse the biomechanical characteristics of four different types of internal fixation to stabilise the posterolateral shearing tibial plateau fracture. Forty synthetic tibiae (Synbone, right) simulated the posterolateral shearing fracture models and these were randomly assigned into four groups; Group A was fixed with two anterolateral lag screws, Group B with an anteromedial Limited Contact Dynamic Compression Plate (LC-DCP), Group C with a lateral locking plate, and Group D with a posterolateral buttress plate. Vertical displacement of the posterolateral fragment was measured using three different strengths of axial loading force, and finally loaded until fixation failure. It was concluded that the posterolateral buttress plate is biomechanically the strongest fixation method for the posterolateral shearing tibial plateau fracture. Copyright © 2011 Elsevier B.V. All rights reserved.

Anatomically precontoured LCP for delayed union of a medial third clavicle fracture. Case report with review of the literature.

PubMed

Siebenlist, S; Sandmann, G; Kirchhoff, C; Biberthaler, P; Neumaier, M

2013-01-01

Fractures of the medial clavicle third are rare injuries. Even in case of significant fracture displacement, their therapeutic management has been nonoperative. Recently, surgical intervention has become mandatory for displaced fractures types to prevent non-union and functional complaints, but the optimal operative strategy is being discussed controversially. We describe the case of a 63-year-old male patient with a significantly displaced medial clavicle fracture after failed conservative treatment resulting in restricted, painful shoulder function. The patient underwent open reduction and osteosynthesis with an anatomically precontoured locking compression plate (LCP). One year after surgery the patient is free of complaints and has returned to his preinjury activity level without any functional restrictions. As a not yet reported operative approach, anatomically preshaped locking plating seems to be an effective fixation method for displaced fractures of the medial clavicle third. The operative management is described in detail and discussed with the current literature. Based on the presented case, we underline the statement that displaced medial clavicle fractures should be surgically addressed to avoid late damage.

Microstructure-failure mode correlations in braided composites

NASA Technical Reports Server (NTRS)

Filatovs, G. J.; Sadler, Robert L.; El-Shiekh, Aly

1992-01-01

Explication of the fracture processes of braided composites is needed for modeling their behavior. Described is a systematic exploration of the relationship between microstructure, loading mode, and micro-failure mechanisms in carbon/epoxy braided composites. The study involved compression and fracture toughness tests and optical and scanning electron fractography, including dynamic in-situ testing. Principal failure mechanisms of low sliding, buckling, and unstable crack growth are correlated to microstructural parameters and loading modes; these are used for defining those microstructural conditions which are strength limiting.

An in vitro study to compare the transverse strength of thermopressed and conventional compression-molded polymethylmethacrylate polymers.

PubMed

Raut, Anjana; Rao, Polsani Laxman; Vikas, B V J; Ravindranath, T; Paradkar, Archana; Malakondaiah, G

2013-01-01

Acrylic resins have been in the center stage of Prosthodontics for more than half a century. The flexural fatigue failure of denture base materials is the primary mode of clinical failure. Hence there is a need for superior physical and mechanical properties. This in vitro study compared the transverse strength of specimens of thermopressed injection-molded and conventional compression-molded polymethylmethacrylate polymers and examined the morphology and microstructure of fractured acrylic specimens. The following denture base resins were examined: Brecrystal (Thermopressed injection-molded, modified polymethylmethacrylate) and Pyrax (compression molded, control group). Specimens of each material were tested according to the American Society for Testing and Materials standard D790-03 for flexural strength testing of reinforced plastics and subsequently examined under SEM. The data was analyzed with Student unpaired t test. Flexural strength of Brecrystal (82.08 ± 1.27 MPa) was significantly higher than Pyrax (72.76 ± 0.97 MPa). The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). The scanning electron microscopy image of Brecrystal revealed a ductile fracture with crazing. The fracture pattern of control group specimens exhibited poorly defined crystallographic planes with a high degree of disorganization. Flexural strength of Brecrystal was significantly higher than the control group. Brecrystal showed a higher mean transverse strength value of 82.08 ± 1.27 MPa and a more homogenous pattern at microscopic level. Based on flexural strength properties and handling characteristics, Brecrystal may prove to be an useful alternative to conventional denture base resins.

Steeply-dipping extension fractures in the Newark basin, New Jersey

USGS Publications Warehouse

Herman, G.C.

2009-01-01

Late Triassic and Early Jurassic bedrock in the Newark basin is pervasively fractured as a result of Mesozoic rifting of the east-central North American continental margin. Tectonic rifting imparted systematic sets of steeply-dipping, en ??chelon, Mode I, extension fractures in basin strata including ordinary joints and veins. These fractures are arranged in transitional-tensional arrays resembling normal dip-slip shear zones. They contributed to crustal stretching, sagging, and eventual faulting of basin rift deposits. Extension fractures display progressive linkage and spatial clustering that probably controlled incipient fault growth. They cluster into three prominent strike groups correlated to early, intermediate, and late-stage tectonic events reflecting about 50- 60?? of counterclockwise rotation of incremental stretching directions. Finite strain analyses show that extension fractures allowed the stretching of basin strata by a few percent, and these fractures impart stratigraphic dips up to a few degrees in directions opposing fracture dips. Fracture groups display three-dimensional spatial variability but consistent geometric relations. Younger fractures locally cut across and terminate against older fractures having more complex vein-cement morphologies and bed-normal folds from stratigraphic compaction. A fourth, youngest group of extension fractures occur sporadically and strike about E-W in obliquely inverted crustal blocks. A geometric analysis of overlapping fracture sets shows how fracture groups result from incremental rotation of an extending tectonic plate, and that old fractures can reactivate with oblique slip components in the contemporary, compressive stress regime. ?? 2008 Elsevier Ltd. All rights reserved.

[Comparison study on locking compress plate external fixator and standard external fixator for treatment of tibial open fractures].

PubMed

Wu, Gang; Luo, Xiaozhong; Tan, Lun; Lin, Xu; Wu, Chao; Guo, Yong; Zhong, Zewei

2013-11-01

To compare the clinical results of locking compress plate (LCP) as an external fixator and standard external fixator for treatment of tibial open fractures. Between May 2009 and June 2012, 59 patients with tibial open fractures were treated with LCP as an external fixator in 36 patients (group A), and with standard external fixator in 23 patients (group B). There was no significant difference in gender, age, cause of injury, affected side, type of fracture, location, and interval between injury and surgery between 2 groups (P > 0.05). The time of fracture healing and incision healing, the time of partial weight-bearing, the range of motion (ROM) of knee and ankle, and complications were compared between 2 groups. The incidence of pin-track infection in group A (0) was significantly lower than that in group B (21.7%) (P=0.007). No significant difference was found in the incidence of superficial infection and deep infection of incision, and the time of incision healing between 2 groups (P > 0.05). Deep vein thrombosis occurred in 5 cases of group A and 2 cases of group B, showing no significant difference (Chi(2)=0.036, P=0.085). All patients were followed up 15.2 months on average (range, 9-28 months) in group A, and 18.6 months on average (range, 9-47 months) in group B. The malunion rate and nonunion rate showed no significant difference between groups A and B (0 versus 13.0% and 0 versus 8.7%, P > 0.05); the delayed union rate of group A (2.8%) was significantly lower than that of group B (21.7%) (Chi(2)=5.573, P=0.018). Group A had shorter time of fracture healing, quicker partial weight-bearing, greater ROM of the knee and ankle than group B (P < 0.05). The LCP external fixator can obtain reliable fixation in treating tibial open fracture, and has good patients' compliance, so it is helpful to do functional exercise, improve fracture healing and function recovery, and reduce the complication incidence.

Fracture development within a stratovolcano: The Karaha-Telaga Bodas geothermal field, Java volcanic arc

USGS Publications Warehouse

Nemcok, M.; Moore, J.N.; Allis, R.; McCulloch, J.

2004-01-01

Karaha-Telaga Bodas, a vapour-dominated geothermal system located in an active volcano in western Java, is penetrated by more than two dozen deep geothermal wells reaching depths of 3 km. Detailed paragenetic and fluid-inclusion studies from over 1000 natural fractures define the liquid-dominated, transitional and vapour-dominated stages in the evolution of this system. The liquid-dominated stage was initiated by ashallow magma intrusion into the base of the volcanic cone. Lava and pyroclastic flows capped a geothermal system. The uppermost andesite flows were only weakly fractured due to the insulating effect of the intervening altered pyroclastics, which absorbed the deformation. Shear and tensile fractures that developed were filled with carbonates at shallow depths, and by quartz, epidote and actinolite at depths and temperatures over 1 km and 300??C. The system underwent numerous cycles of overpressuring, documented by subhorizontal tensile fractures, anastomosing tensile fracture patterns and implosion breccias. The development of the liquidsystem was interrupted by a catastrophic drop in fluid pressures. As the fluids boiled in response to this pressure drop, chalcedony and quartz were selectively deposited in fractures that had the largest apertures and steep dips. The orientations of these fractures indicate that the escaping overpressured fluids used the shortest possible paths to the surface. Vapour-dominated conditions were initiated at this time within a vertical chimney overlying the still hot intrusion. As pressures declined, these conditions spread outward to form the marginal vapour-dominated region encountered in the drill holes. Downward migration of the chimney, accompanied by growth of the marginal vapour-dominated regime, occurred as the intrusion cooled and the brittle-ductile transition migrated to greater depths. As the liquids boiled off, condensate that formed at the top of the vapour-dominated zone percolated downward and low-salinity meteoric water entered the marginal parts of the system. Calcite, anhydrite and fluorite precipitated in fractures on heating. Progressive sealing of the fractures resulted in the downward migration of the cap rock. In response to decreased pore pressure in the expanding vapour zone, walls of the fracture system within the vapour-dominated reservoir progressively collapsed. It left only residual permeability in the remaining fracture volume, with apertures supported only by asperities or propping breccia. In places where normal stresses acting on the fracture walls exceeded the compressive strength of the wall rock, the fractures have completely collapsed. Fractures within the present-day cap rock include strike- and oblique-slip faults, normal faults and tensile fractures, all controlled by a strike-slip stress regime. The reservoir is characterized by normal faults and tensile fractures controlled by a normal-fault stress regime. The fractures show no evidence that the orientation of the stress field has changed since fracture propagation began. Fluid migration in the lava and pyroclastic flows is controlled by fractures. Matrix permeability controls fluid flow in the sedimentary sections of the reservoir. Productive fractures are typically roughly perpendicular to the minimum compressive stress, ??3, and are prone to slip and dilation within the modern stress regime. ?? The Geological Society of London 2004.

Atlas Fractures and Atlas Osteosynthesis: A Comprehensive Narrative Review.

PubMed

Kandziora, Frank; Chapman, Jens R; Vaccaro, Alexander R; Schroeder, Gregory D; Scholz, Matti

2017-09-01

Most atlas fractures are the result of compression forces. They are often combined with fractures of the axis and especially with the odontoid process. Multiple classification systems for atlas fractures have been described. For an adequate diagnosis, a computed tomography is mandatory. To distinguish between stable and unstable atlas injury, it is necessary to evaluate the integrity of the transverse atlantal ligament (TAL) by magnetic resonance imaging and to classify the TAL lesion. Studies comparing conservative and operative management of unstable atlas fractures are unfortunately not available in the literature; neither are studies comparing different operative treatment strategies. Hence all treatment recommendations are based on low level evidence. Most of atlas fractures are stable and will be successfully managed by immobilization in a soft/hard collar. Unstable atlas fractures may be treated conservatively by halo-fixation, but nowadays more and more surgeons prefer surgery because of the potential discomfort and complications of halo-traction. Atlas fractures with a midsubstance ligamentous disruption of TAL or severe bony ligamentous avulsion can be treated by a C1/2 fusion. Unstable atlas fractures with moderate bony ligamentous avulsion may be treated by atlas osteosynthesis. Although the evidence for the different treatment strategies of atlas fractures is low, atlas osteosynthesis has the potential to change treatment philosophies. The reasons for this are described in this review.

Microscopic Characterization of Tensile and Shear Fracturing in Progressive Failure in Marble

NASA Astrophysics Data System (ADS)

Cheng, Yi; Wong, Louis Ngai Yuen

2018-01-01

Compression-induced tensile and shear fractures were reported to be the two fundamental fracture types in rock fracturing tests. This study investigates such tensile and shear fracturing process in marble specimens containing two different flaw configurations. Observations first reveal that the development of a tensile fracture is distinct from shear fracture with respect to their nucleation, propagation, and eventual formation in macroscale. Second, transgranular cracks and grain-scale spallings become increasingly abundant in shear fractures as loading increases, which is almost not observed in tensile fractures. Third, one or some dominant extensional microcracks are commonly observed in the center of tensile fractures, while such development of microcracks is almost absent in shear fractures. Microcracks are generally of a length comparable to grain size and distribute uniformly within the damage zone of the shear fracture. Fourth, the width of densely damaged zone in the shear fracture is nearly 10 times of that in the tensile fracture. Quantitative measurement on microcrack density suggests that (1) microcrack density in tensile and shear fractures display distinct characteristics with increasing loading, (2) transgranular crack density in the shear fracture decreases logarithmically with the distance away from the shear fracture center, and (3) whatever the fracture type, the anisotropy can only be observed for transgranular cracks with a large density, which partially explains why microcrack anisotropy usually tends to be unobvious until approaching peak stress in specimens undergoing brittle failure. Microcracking characteristics observed in this work likely shed light to some phenomena and conclusions generalized in seismological studies.

Stability and Process of Destruction of Compressed Plate of Layered Composite Materials With Defects

NASA Astrophysics Data System (ADS)

Bokhoeva, L. A.; Rogov, V. E.; Chermoshentseva, A. S.; Lobanov, D. V.

2016-08-01

Interlayer defects in composite materials are a pressing problem, which affecting their performance characteristics. In this research, we considered the problem of the stability and of the fracture process of the compressed thin plate made of laminated composite materials with the interlayer defects. In this research we had got a critical equation for a plate with interlayer defect. The experiment showed the effect and the quantity of nano-dispersed additives on the mechanical properties of composite materials with interlayer defects.

Preventing and Treating Compression Fractures of the Spine

MedlinePlus

... 210 Gaithersburg, MD 20878 (800) 981-2663 (301) 947-0083 Fax: (301) 947-0456 Internet: www.oif.org Email: bonelink@oif. ... 800-981-2663 (free of charge) or 301-947-0083 Fax: 301-947-0456 Internet: www.oif. ...

Functional outcome of displaced intra-articular calcaneal fractures: a comparison between open reduction/internal fixation and a minimally invasive approach featured an anatomical plate and compression bolts.

PubMed

Wu, Zhanpo; Su, Yanling; Chen, Wei; Zhang, Qi; Liu, Yueju; Li, Ming; Wang, Haili; Zhang, Yingze

2012-09-01

The purpose of this study is to assess the clinical results of a minimally invasive treatment featured the concept of internal compression, including an anatomic plate and multiple compression bolts compared with open reduction and internal fixation for displaced intra-articular calcaneal fractures (DIACFs). We retrospectively analyzed 329 patients (383 feet) who were identified from trauma inpatient database in our hospital for DIACFs from January 2004 to December 2009. Of them, 148 patients (170 feet) were treated with open reduction and internal fixation (OR group), which involved using a traditional L-shaped extended lateral approach, and fractures were fixed by plate and screws from January 2004 to December 2006; 181 patients (213 feet) were treated with a minimally invasive approach featured the concept of calcaneal internal compression (CIC group), which was achieved by an anatomic plate and multiple compression bolts through a small lateral incision from January 2007 to December 2009. Postoperative complications were recorded. During follow-up, pain and functional outcome were evaluated with the American Orthopaedic Foot and Ankle Society (AOFAS) scores and compared between the two groups. Subsequent subtalar arthrodesis and early implant removal were performed when indicated. Routine hardware removal was scheduled for all patients at 1-year follow-up. There were no significant differences in sex, age, and fracture classification (Sanders classification) between the two groups. Wound healing complications were 4 of 213 (1.88%) in CIC group and 20 of 170 (11.76%) in OR group. Subtalar arthrodesis had to be performed in one case in OR group. Four cases in CIC group and four cases in OR group had the hardware removed earlier due to complications. The average time after surgery to start weight-bearing exercise is 5.64 weeks in CIC group and 9.38 weeks in OR group (p < 0.001). The mean AOFAS score is higher in CIC group than in OR group, although the difference is not statistically significant (87.53 vs. 84.95; p = 0.191). The overall results according to the AOFAS scoring system were good or excellent in 185 of 213 (86.85%) in CIC group and 144 of 170 (84.71%) in OR group. The subjective portion of the AOFAS survey answered by patients showed statistically significant difference in activity limitation and walking surface score (7.31 vs. 7.02 and 3.72 vs. 3.42; p < 0.05) but not in pain and walking distance between the two groups (32.72 vs. 32.29 and 4.37 vs. 4.42; p > 0.05). The study results suggest that this minimally invasive approach featured the concept of the calcaneal internal compression can achieve functional outcome as good as, if not better than the open techniques. It is proved to be an effective alternative treatment for DIACFs. Therapeutic study, level IV.

Fractographic examination of racing greyhound central (navicular) tarsal bone failure surfaces using scanning electron microscopy.

PubMed

Tomlin, J L; Lawes, T J; Blunn, G W; Goodship, A E; Muir, P

2000-09-01

The greyhound is a fatigue fracture model of a short distance running athlete. Greyhounds have a high incidence of central (navicular) tarsal bone (CTB) fractures, which are not associated with overt trauma. We wished to determine whether these fractures occur because of accumulation of fatigue microdamage. We hypothesized that bone from racing dogs would show site-specific microdamage accumulation, causing predisposition to structural failure. We performed a fractographic examination of failure surfaces from fractured bones using scanning electron microscopy and assessed microcracking observed at the failure surface using a visual analog scale. Branching arrays of microcracks were seen in failure surfaces of CTB and adjacent tarsal bones, suggestive of compressive fatigue failure. Branching arrays of microcracks were particularly prevalent in remodeled trabecular bone that had become compact. CTB fractures showed increased microdamage when compared with other in vivo fractures (adjacent tarsal bone and long bone fractures), and ex vivo tarsal fractures induced by monotonic loading (P < 0.02). It was concluded that greyhound racing and training often results in CTB structural failure, because of accumulation and coalescence of branching arrays of fatigue microcracks, the formation of which appears to be predisposed to adapted bone.

Compositional Reservoir Simulation of Highly Heterogeneous and Anisotropic Fractured Media in 2D and 3D Unstructured Gridding

NASA Astrophysics Data System (ADS)

Zidane, A.; Firoozabadi, A.

2017-12-01

We present an efficient and accurate numerical model for multicomponent compressible single-phase flow in 2D and 3D fractured media based on higher-order discretization. The numerical model accounts for heterogeneity and anisotropy in unstructured gridding with low mesh dependency. The efficiency of our model is demonstrated by having comparable CPU time between fractured and unfractured media. The fracture cross-flow equilibrium approach (FCFE) is applied on triangular finite elements (FE) in 2D. This allows simulating fractured reservoirs with all possible orientations of fractures as opposed to rectangular FE. In 3D we apply the FCFE approach on the prism FE. The prism FE with FCFE allows simulating realistic fractured domains compared to hexahedron FE. In addition, when using FCFE on triangular and prism FE there is no limitation on the number of intersecting fractures, whereas in rectangular and hexahedron FE the number is limited to 2 in 2D and 3 in 3D. To generate domains with complicated boundaries, we have developed a computer-aided design (CAD) interface in our model. The advances introduced in this work are demonstrated through various examples.

Use of the S3 Corridor for Iliosacral Fixation in a Dysmorphic Sacrum: A Case Report.

PubMed

El Dafrawy, Mostafa H; Strike, Sophia A; Osgood, Greg M

2017-01-01

The S1 and S2 corridors are the typical osseous pathways for iliosacral screw fixation of posterior pelvic ring fractures. In dysmorphic sacra, the S1 screw trajectory is often different from that in normal sacra. We present a case of iliosacral screw placement in the third sacral segment for fixation of a complex lateral compression type-3 pelvic fracture in a patient with a dysmorphic sacrum. In patients with dysmorphic sacra and unstable posterior pelvic ring fractures or dislocations, the S3 corridor may be a feasible osseous fixation pathway that can be used in a manner equivalent to the S2 corridor in a normal sacrum.

Comparative review of vertebroplasty and kyphoplasty

PubMed Central

Ruiz Santiago, Fernando; Santiago Chinchilla, Alicia; Guzmán Álvarez, Luis; Pérez Abela, Antonio Luis; Castellano García, Maria del Mar; Pajares López, Miguel

2014-01-01

The aim of this review is to compare the effectiveness of percutaneous vertebroplasty and kyphoplasty to treat pain and improve functional outcome from vertebral fractures secondary to osteoporosis and tumor conditions. In 2009, two open randomized controlled trials published in the New England Journal of Medicine questioned the value of vertebroplasty in treating vertebral compression fractures. Nevertheless, the practice of physicians treating these conditions has barely changed. The objective of this review is to try to clarify the most important issues, based on our own experience and the reported evidence about both techniques, and to guide towards the most appropriate choice of treatment of vertebral fractures, although many questions still remain unanswered. PMID:24976934

Cracking mechanism of shale cracks during fracturing

NASA Astrophysics Data System (ADS)

Zhao, X. J.; Zhan, Q.; Fan, H.; Zhao, H. B.; An, F. J.

2018-06-01

In this paper, we set up a model for calculating the shale fracture pressure on the basis of Huang’s model by the theory of elastic-plastic mechanics, rock mechanics and the application of the maximum tensile stress criterion, which takes into account such factors as the crustal stress field, chemical field, temperature field, tectonic stress field, the porosity of shale and seepage of drilling fluid and so on. Combined with the experimental data of field fracturing and the experimental results of three axis compression of shale core with different water contents, the results show that the error between the present study and the measured value is 3.85%, so the present study can provide technical support for drilling engineering.

Non-invasive measurement of proppant pack deformation

DOE PAGES

Walsh, Stuart D. C.; Smith, Megan; Carroll, Susan A.; ...

2016-05-26

In this study, we describe a method to non-invasively study the movement of proppant packs at the sub-fracture scale by applying three-dimensional digital image correlation techniques to X-ray tomography data. Proppant movement is tracked in a fractured core of Marcellus shale placed under a series of increasing confining pressures up to 10,000 psi. The analysis reveals the sudden failure of a region of the proppant pack, accompanied by the large-scale rearrangement of grains across the entire fracture surface. The failure of the pack coincides with the appearance of vortex-like grain motions similar to features observed in biaxial compression of twomore » dimensional granular assemblies.« less

Defect nonunion of a metatarsal bone fracture in a cow: successful management with bone plating and autogenous cancellous bone graft.

PubMed

Raghunath, M; Singh, N; Singh, T; Gopinathan, A; Mohindroo, J; Atri, K

2013-01-01

A two-and-half-year-old cow was presented with a defect nonunion of the right metatarsal III/IV bone following a severely comminuted open fracture two months previously. The animal underwent open fixation using a 4.5 mm, broad, 10-hole, dynamic compression plate and autogenous cancellous bone graft collected from the contralateral iliac shaft. The animal started partial weight bearing after the third postoperative day and resumed complete weight bearing after the 10th day. Fracture healing was complete and the implants were removed after the 120th postoperative day. Stable fixation by means of a bone plate in conjunction with a cancellous bone graft facilitated complete healing and restoration of the bone column of the defect and the metatarsal fracture. The animal made a complete recovery.

Hydraulic fracturing in cells and tissues: fracking meets cell biology.

PubMed

Arroyo, Marino; Trepat, Xavier

2017-02-01

The animal body is largely made of water. A small fraction of body water is freely flowing in blood and lymph, but most of it is trapped in hydrogels such as the extracellular matrix (ECM), the cytoskeleton, and chromatin. Besides providing a medium for biological molecules to diffuse, water trapped in hydrogels plays a fundamental mechanical role. This role is well captured by the theory of poroelasticity, which explains how any deformation applied to a hydrogel causes pressure gradients and water flows, much like compressing a sponge squeezes water out of it. Here we review recent evidence that poroelastic pressures and flows can fracture essential biological barriers such as the nuclear envelope, the cellular cortex, and epithelial layers. This type of fracture is known in engineering literature as hydraulic fracturing or 'fracking'. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of Two Miniplate Systems and Figure-of-eight Bandages for Stabilization of Experimentally Induced Ulnar and Radial Fractures in Pigeons ( Columba livia ).

PubMed

Bennert, Beatrice M; Kircher, Patrick R; Gutbrod, Andreas; Riechert, Juliane; Hatt, Jean-Michel

2016-06-01

Although plate fixation has advantages over other fixation methods for certain indications, it is rarely used in avian surgery, especially in birds that weigh less than 1000 g. Exceptionally small plating systems for these birds are required, which are relatively expensive and difficult to insert. To study avian fracture healing after repair using miniplates, we evaluated 2 steel miniplate systems in 27 pigeons ( Columba livia ) divided into 4 groups. In each pigeon, the left ulna and radius were transected and the ulna was repaired with a bone plate. In groups A and B, a 1.3-mm adaption plate was applied without and with a figure-of-eight bandage; in groups C and D, a 1.0-mm compression plate was applied without and with a bandage, respectively. Healing was evaluated with radiographs after 3, 14, and 28 days; flight tests were conducted after 14, 21, and 28 days; and the wing was macroscopically examined after euthanasia of birds on day 28. Fractures healed without bending or distortion of the plate in all 27 birds, and no significant differences in healing were found between treatment groups. At the end of the study, 23 pigeons (85.2%) showed good or very good flight ability. Results show the 1.3-mm adaption plate and the 1.0-mm compression plate meet the requirements for avian osteosynthesis and can be recommended for fracture repair of the ulna or other long bones in birds weighing less than 500 g. The application of a figure-of-eight bandage might be beneficial in fracture healing.

Virtual stress testing of fracture stability in soldiers with severely comminuted tibial fractures.

PubMed

Petfield, Joseph L; Hayeck, Garry T; Kopperdahl, David L; Nesti, Leon J; Keaveny, Tony M; Hsu, Joseph R

2017-04-01

Virtual stress testing (VST) provides a non-invasive estimate of the strength of a healing bone through a biomechanical analysis of a patient's computed tomography (CT) scan. We asked whether VST could improve management of patients who had a tibia fracture treated with external fixation. In a retrospective case-control study of 65 soldier-patients who had tibia fractures treated with an external fixator, we performed VST utilizing CT scans acquired prior to fixator removal. The strength of the healing bone and the amount of tissue damage after application of an overload were computed for various virtual loading cases. Logistic regression identified computed outcomes with the strongest association to clinical events related to nonunion within 2 months after fixator removal. Clinical events (n = 9) were associated with a low tibial strength for compression loading (p < 0.05, AUC = 0.74) or a low proportion of failed cortical bone tissue for torsional loading (p < 0.005, AUC = 0.84). Using post-hoc thresholds of a compressive strength of four times body-weight and a proportional of failed cortical bone tissue of 5%, the test identified all nine patients who failed clinically (100% sensitivity; 40.9% positive predictive value) and over three fourths of those (43 of 56) who progressed to successful healing (76.8% specificity; 100% negative predictive value). In this study, VST identified all patients who progressed to full, uneventful union after fixator removal; thus, we conclude that this new test has the potential to provide a quantitative, objective means of identifying tibia-fracture patients who can safely resume weight bearing. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:805-811, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Investigation of motorcyclist cervical spine trauma using HUMOS model.

PubMed

Sun, Jingchao; Rojas, Alban; Bertrand, Pierre; Petit, Yvan; Kraenzler, Reinhard; Arnoux, Pierre Jean

2012-09-01

With 16 percent of the total road user fatalities, motorcyclists represent the second highest rate of road fatalities in France after car occupants. Regarding road accidents, a large proportion of trauma was on the lower cervical spine. According to different clinical studies, it is postulated that the cervical spine fragility areas are located on the upper and lower cervical spine. In motorcycle crashes, impact conditions occur on the head segment with various orientations and impact directions, leading to a combination of rotations and compression. Hence, motorcyclist vulnerability was investigated considering many impact conditions. Using the human model for safety (HUMOS), a finite element model, this work aims to provide an evaluation of the cervical spine weaknesses based on an evaluation of injury mechanisms. This evaluation consisted of defining 2 injury risk factors (joint injury and bone fracture) using a design of experiment including various velocities, impact directions, and impact orientations. The results confirmed previously reported clinical and epidemiological work on the fragility of the lower cervical spine and the upper cervical spine segments. Joint injuries appeared before bone fractures on both the upper and lower cervical spine. Bone fracture risk was greater on the lower cervical spine than on the upper cervical spine. The compression induced by a high impact angle was identified as an important injury severity factor. It significantly increased the injury incidence for both joint injuries and bone fractures. It also induced a shift in injury location from the lower to the upper cervical spine. The impact velocity exhibited a linear relationship with injury risks and severity. It also shifted the bone fracture risk from the lower to upper spinal segments.

Influence of Composition and Deformation Conditions on the Strength and Brittleness of Shale Rock

NASA Astrophysics Data System (ADS)

Rybacki, E.; Reinicke, A.; Meier, T.; Makasi, M.; Dresen, G. H.

2015-12-01

Stimulation of shale gas reservoirs by hydraulic fracturing operations aims to increase the production rate by increasing the rock surface connected to the borehole. Prospective shales are often believed to display high strength and brittleness to decrease the breakdown pressure required to (re-) initiate a fracture as well as slow healing of natural and hydraulically induced fractures to increase the lifetime of the fracture network. Laboratory deformation tests were performed on several, mainly European black shales with different mineralogical composition, porosity and maturity at ambient and elevated pressures and temperatures. Mechanical properties such as compressive strength and elastic moduli strongly depend on shale composition, porosity, water content, structural anisotropy, and on pressure (P) and temperature (T) conditions, but less on strain rate. We observed a transition from brittle to semibrittle deformation at high P-T conditions, in particular for high porosity shales. At given P-T conditions, the variation of compressive strength and Young's modulus with composition can be roughly estimated from the volumetric proportion of all components including organic matter and pores. We determined also brittleness index values based on pre-failure deformation behavior, Young's modulus and bulk composition. At low P-T conditions, where samples showed pronounced post-failure weakening, brittleness may be empirically estimated from bulk composition or Young's modulus. Similar to strength, at given P-T conditions, brittleness depends on the fraction of all components and not the amount of a specific component, e.g. clays, alone. Beside strength and brittleness, knowledge of the long term creep properties of shales is required to estimate in-situ stress anisotropy and the healing of (propped) hydraulic fractures.

Novel compound heterozygous mutations in SERPINH1 cause rare autosomal recessive osteogenesis imperfecta type X.

PubMed

Song, Y; Zhao, D; Xu, X; Lv, F; Li, L; Jiang, Y; Wang, O; Xia, W; Xing, X; Li, M

2018-03-09

We identified novel compound heterozygous mutations in SERPINH1 in a Chinese boy suffering from recurrent fractures, femoral deformities, and growth retardation, which resulted in extremely rare autosomal recessive OI type X. Long-term treatment of BPs was effective in increasing BMD Z-score, reducing fracture incidence and reshaping vertebrae compression. Osteogenesis imperfecta (OI) is a heritable bone disorder characterized by low bone mineral density, recurrent fractures, and progressive bone deformities. Mutation in serpin peptidase inhibitor clade H, member 1 (SERPINH1), which encodes heat shock protein 47 (HSP47), leads to rare autosomal recessive OI type X. We aimed to detect the phenotype and the pathogenic mutation of OI type X in a boy from a non-consanguineous Chinese family. We investigated the pathogenic mutations and analyzed their relationship with the phenotype in the patient using next-generation sequencing (NGS) and Sanger sequencing. Moreover, the efficacy of long-term bisphosphonate treatment in this patient was evaluated. The patient suffered from multiple fractures, low bone mass, and bone deformities in the femur, without dentinogenesis imperfecta or hearing loss. Compound heterozygous variants were found in SERPINH1 as follows: c.149 T>G in exon 2 and c.1214G>A in exon 5. His parents were heterozygous carriers of each of these mutations, respectively. Bisphosphonates could be helpful in increasing BMD Z-score, reducing bone fracture risk and reshaping the compressed vertebral bodies of this patient. We reported novel compound heterozygous mutations in SERPINH1 in a Chinese OI patient for the first time, which expanded the spectrum of phenotype and genotype of extremely rare OI type X.

Percutaneous osteoplasty with a bone marrow nail for fractures of long bones: experimental study.

PubMed

Nakata, Kouhei; Kawai, Nobuyuki; Sato, Morio; Cao, Guang; Sahara, Shinya; Tanihata, Hirohiko; Takasaka, Isao; Minamiguchi, Hiroyuki; Nakai, Tomoki

2010-09-01

To develop percutaneous osteoplasty with the use of a bone marrow nail for fixation of long-bone fractures, and to evaluate its feasibility and safety in vivo and in vitro. Six long bones in three healthy swine were used in the in vivo study. Acrylic cement was injected through an 11-gauge bone biopsy needle and a catheter into a covered metallic stent placed within the long bone, creating a bone marrow nail. In the in vitro study, we determined the bending, tug, and compression strengths of the acrylic cement nails 9 cm long and 8 mm in diameter (N = 10). The bending strength of the artificially fractured bones (N = 6) restored with the bone marrow nail and cement augmentation was then compared with that of normal long bones (N = 6). Percutaneous osteoplasty with a bone marrow nail was successfully achieved within 1 hour for all swine. After osteoplasty, all swine regained the ability to run until they were euthanized. Blood tests and pathologic findings showed no adverse effects. The mean bending, tug, and compression strengths of the nail were 91.4 N/mm(2) (range, 75.0-114.1 N/mm(2)), 20.9 N/mm(2) (range, 6.6-30.4 N/mm(2)), and 103.0 N/mm(2) (range, 96.3-110.0 N/mm(2)), respectively. The bending strength ratio of artificially fractured bones restored with bone marrow nail and cement augmentation to normal long bone was 0.32. Percutaneous osteoplasty with use of a bone marrow nail and cement augmentation appears to have potential in treating fractures of non-weight-bearing long bones. Copyright 2010 SIR. Published by Elsevier Inc. All rights reserved.

Fractured Rock Permeability as a Function of Temperature and Confining Pressure

NASA Astrophysics Data System (ADS)

Alam, A. K. M. Badrul; Fujii, Yoshiaki; Fukuda, Daisuke; Kodama, Jun-ichi; Kaneko, Katsuhiko

2015-10-01

Triaxial compression tests were carried out on Shikotsu welded tuff, Kimachi sandstone, and Inada granite under confining pressures of 1-15 MPa at 295 and 353 K. The permeability of the tuff declined monotonically with axial compression. The post-compression permeability became smaller than that before axial compression. The permeability of Kimachi sandstone and Inada granite declined at first, then began to increase before the peak load, and showed values that were almost constant in the residual strength state. The post-compression permeability of Kimachi sandstone was higher than that before axial compression under low confining pressures, but lower under higher confining pressures. On the other hand, the permeability of Inada granite was higher than that before axial compression regardless of the confining pressure values. For the all rock types, the post-compression permeability at 353 K was lower than at 295 K and the influence of the confining pressure was less at 353 K than at 295 K. The above temperature effects were observed apparently for Inada granite, only the latter effect was apparent for Shikotsu welded tuff, and they were not so obvious for Kimachi sandstone. The mechanisms causing the variation in rock permeability and sealability of underground openings were discussed.

Fracture simulation of restored teeth using a continuum damage mechanics failure model.

PubMed

Li, Haiyan; Li, Jianying; Zou, Zhenmin; Fok, Alex Siu-Lun

2011-07-01

The aim of this paper is to validate the use of a finite-element (FE) based continuum damage mechanics (CDM) failure model to simulate the debonding and fracture of restored teeth. Fracture testing of plastic model teeth, with or without a standard Class-II MOD (mesial-occusal-distal) restoration, was carried out to investigate their fracture behavior. In parallel, 2D FE models of the teeth are constructed and analyzed using the commercial FE software ABAQUS. A CDM failure model, implemented into ABAQUS via the user element subroutine (UEL), is used to simulate the debonding and/or final fracture of the model teeth under a compressive load. The material parameters needed for the CDM model to simulate fracture are obtained through separate mechanical tests. The predicted results are then compared with the experimental data of the fracture tests to validate the failure model. The failure processes of the intact and restored model teeth are successfully reproduced by the simulation. However, the fracture parameters obtained from testing small specimens need to be adjusted to account for the size effect. The results indicate that the CDM model is a viable model for the prediction of debonding and fracture in dental restorations. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Hydromechanics in dentine: role of dentinal tubules and hydrostatic pressure on mechanical stress-strain distribution.

PubMed

Kishen, A; Vedantam, S

2007-10-01

This investigation is to understand the role of free water in the dentinal tubules on the mechanical integrity of bulk dentine. Three different experiments were conducted in this study. In experiment 1, three-dimensional models of dentine with gradient elastic modulus, homogenous elastic modulus, and with and without hydrostatic pressure were simulated using the finite element method. Static compressive loads of 15, 50 and 100 N were applied and the distribution of the principal stresses, von Mises stresses, and strains in loading direction were determined. In experiment 2, experimental compression testing of fully hydrated and partially dehydrated dentine (21 degrees C for 72 h) was conducted using a Universal testing machine. In experiment 3, Fourier transform infrared spectroscopic analysis of hydrated and partially dehydrated dentine was carried out. The finite element analysis revealed that the dentine model with simulated hydrostatic pressure displayed residual tensile stresses and strains in the inner region adjacent to the root canal. When external compressive loads were applied to the model, the residual stresses and strains counteracted the applied loads. Similarly the hydrated specimens subjected to experimental compression loads showed greater toughness when compared to the partially dehydrated specimens. The stress at fracture was significantly higher in partially dehydrated specimens (p=0.014), while the strain at fracture was significantly higher in hydrated dentine specimens (p=0.037). These experiments highlighted the distinct role of free water in the dentinal tubules and hydrostatic pressure on the stress-strain distribution within the bulk dentine.

Role of large-scale slip in mode II fracture of bimaterial interface produced by diffusion bonding

NASA Astrophysics Data System (ADS)

Fox, M. R.; Ghosh, A. K.

2001-08-01

Bimaterial interfaces present in diffusion-bonded (and in-situ) composites are often not flat interfaces. The unevenness of the interface can result not only from interface reaction products but also from long-range waviness associated with the surfaces of the component phases bonded together. Experimental studies aimed at determining interface mechanical properties generally ignore the departure in the local stress due to waviness and assume a theoretically flat interface. Furthermore, the commonly used testing methods involving superimposed tension often renders the interface so extremely brittle that if microplastic effects were present it becomes impossible to perceive them. This article examines the role of waviness of the interface and microplastic effects on crack initiation. To do this, a test was selected that provides significant stability against crack growth by superimposing compressive stresses. Mode II interface fracture was studied for NiAl/Mo model laminates using a recently developed asymmetrically loaded shear (ALS) interface shear test. The ALS test may be viewed as opposite of the laminate bend test. In the bend test, shear at the interface is created via tension on one surface of the bend, while in the ALS test, shear is created by compression on one side of the interface relative to the other. Normal to the interface, near the crack tip, an initially compressive state is replaced by slight tension due to Poisson’s expansion of the unbonded part of the compressed beam.

Height restoration of osteoporotic vertebral compression fractures using different intravertebral reduction devices: a cadaveric study.

PubMed

Krüger, Antonio; Oberkircher, Ludwig; Figiel, Jens; Floßdorf, Felix; Bolzinger, Florent; Noriega, David C; Ruchholtz, Steffen

2015-05-01

The treatment of osteoporotic vertebral compression fractures using transpedicular cement augmentation has grown significantly during the past two decades. Balloon kyphoplasty was developed to restore vertebral height and improve sagittal alignment. Several studies have shown these theoretical improvements cannot be transferred universally to the clinical setting. The aim of the current study is to evaluate two different procedures used for percutaneous augmentation of vertebral compression fractures with respect to height restoration: balloon kyphoplasty and SpineJack. Twenty-four vertebral bodies of two intact, fresh human cadaveric spines (T6-L5; donor age, 70 years and 60 years; T-score -6.8 points and -6.3 points) were scanned using computed tomography (CT) and dissected into single vertebral bodies. Vertebral wedge compression fractures were created by a material testing machine (Universal testing machine, Instron 5566, Darmstadt, Germany). The axial load was increased continuously until the height of the anterior edge of the vertebral body was reduced by 40% of the initial measured values. After 15 minutes, the load was decreased manually to 100 N. After postfracture CT, the clamped vertebral bodies were placed in a custom-made loading frame with a preload of 100 N. Twelve vertebral bodies were treated using SpineJack (SJ; Vexim, Balma, France), the 12 remaining vertebral bodies were treated with balloon kyphoplasty (BKP; Kyphon, Medtronic, Sunnyvale, CA, USA). The load was maintained during the procedure until the cement set completely. Posttreatment CT was performed. Anterior, central, and posterior height as well as the Beck index were measured prefracture and postfracture as well as after treatment. For anterior height restoration (BKP, 0.14±1.48 mm; SJ, 3.34±1.19 mm), central height restoration (BKP, 0.91±1.04 mm; SJ, 3.24±1.22 mm), and posterior restoration (BKP, 0.37±0.57 mm; SJ, 1.26±1.05), as well as the Beck index (BKP, 0.00±0.06 mm; SJ, 0.10±0.06), the values for the SpineJack group were significantly higher (p<.05) CONCLUSION: The protocols for creating wedge fractures and using the instrumentation under a constant preload of 100 N led to reproducible results and effects. The study showed that height restoration was significantly better in the SpineJack group compared with the balloon kyphoplasty group. The clinical implications include a better restoration of the sagittal balance of the spine and a reduction of the kyphotic deformity, which may relate to clinical outcome and the biological healing process. Copyright © 2015 Elsevier Inc. All rights reserved.

Four dimensional X-ray imaging of deformation modes in organic-rich Green River Shale retorted under uniaxial compression

NASA Astrophysics Data System (ADS)

Kobchenko, M.; Pluymakers, A.; Cordonnier, B.; Tairova, A.; Renard, F.

2017-12-01

Time-lapse imaging of fracture network development in organic-rich shales at elevated temperatures while kerogen is retorted allows characterizing the development of microfractures and the onset of primary migration. When the solid organic matter is transformed to hydrocarbons with lower molecular weight, the local pore-pressure increases and drives the propagation of hydro-fractures sub-parallel to the shale lamination. On the scale of samples of several mm size, these fractures can be described as mode I opening, where fracture walls dilate in the direction of minimal compression. However, so far experiments coupled to microtomography in situ imaging have been performed on samples where no load was imposed. Here, an external load was applied perpendicular to the sample laminations and we show that this stress state slows down, but does not stop, the propagation of fracture along bedding. Conversely, microfractures also propagate sub-perpendicular to the shale lamination, creating a percolating network in three dimensions. To monitor this process we have used a uniaxial compaction rig combined with in-situ heating from 50 to 500 deg C, while capturing three-dimensional X-ray microtomography scans at a voxel resolution of 2.2 μm; Data were acquired at beamline ID19 at the European Synchrotron Radiation Facility. In total ten time-resolved experiments were performed at different vertical loading conditions, with and without lateral passive confinement and different heating rates. At high external load the sample fails by symmetric bulging, while at lower external load the reaction-induced fracture network develops with the presence of microfractures both sub-parallel and sub-perpendicular to the bedding direction. In addition, the variation of experimental conditions allows the decoupling of the effects of the hydrocarbon decomposition reaction on the deformation process from the influence of thermal stress heating on the weakening and failure mode of immature shale.

Evaluation of In-Situ Stress Assessment from Deep Borehole in the Middle Coastal Plain and Its implication for Taiwan Tectonics

NASA Astrophysics Data System (ADS)

Yeh, E. C.; Li, W. C.; Chiang, T. C.; Lin, W.; Wang, T. T.; Yu, C. W.; Chiao, C. H.; Yang, M. W.

2014-12-01

Scientific study in deep boreholes has paid more attention as the demand of natural resources and waste disposal and risk evaluation of seismic hazard dramatically increases, such as petroleum exploitation, geothermal energy, carbon sequestration, nuclear waste disposal and seismogenic faulting. In the deep borehole geoengineering, knowledge of in-situ stress is essential for the design of drilling-casing plan. Understanding the relationship between fracture and in-situ stress is the key information to evaluate the potential of fracture seal/conduit and fracture reactivity. Also, assessment of in-situ stress can provide crucial information to investigate mechanism of earthquake faulting and stress variationfor earthquake cycles. Formations under the Coastal Plain in Taiwan have evaluated as saline-water formations with gently west-dipping and no distinct fractures endured by regional tectonics of arc-continental collision with N35W compression. The situation is characterized as a suitable place for carbon sequestration. In this study, we will integrate results from different in-situ stress determinations such as anelastic strain recovery (ASR), borehore breakout, hydraulic fracturing from a 3000m borehole of carbon sequestration testing site and further evaluate the seal feasibility and tectonic implication. Results of 30 ASR experiments between the depth of 1500m and 3000m showed the consistent normal faulting stress regime. Stress gradient of vertical stress, horizontal maximum stress and horizontal minimum stress with depth is estimated. Borehole breakout is not existed throughout 1500-3000m. The mean orientation of breakout is about 175deg and mean width of breakout is 84 deg. Based on rock mechanical data, maximum injection pressure of carbon sequestration can be evaulated. Furthermore, normal faulting stress regime is consistent with core observations and image logging, the horizontal maximum stress of 85deg inferred from breakout suggested that this place has been affected by the compression of oblique collision. The comparison of stress magnitudes estimated from ASR, breakout and hydraulic fracturing cab further verified current results.

Haemodynamically Unstable Pelvic Fractures

DTIC Science & Technology

2009-01-01

through the pubic symphysis, and posteriorlywith the sacrum forming the sacroiliac (SI) joints (Fig. 1). The SI joints are the strongest in the body...Gardner MJ, Kendoff D, Ostermeier S, et al. Sacroiliac joint compression using an anterior pelvic compressor: a mechanical study in synthetic bone. J

The importance of pelvic ring stabilization as a life-saving measure in pre-hospital - A case report commented by autopsy.

PubMed

Durão, Carlos; Alves, Magda; Barros, André; Pedrosa, Frederico

2017-08-01

Hip fractures with unstable pelvic ring have great morbidity and mortality rates. These fractures result from high energy trauma such as falls from heights, road accidents and collapsing structures or other similar mechanisms of action. We report the case of a 63 years old man, construction worker, who stood inside a ditch during a wall construction when he was surprised by this collapse, which resulted in direct trauma to the right thigh and pelvis. The autopsy revealed diaphysis fracture of the right femur with an open book pelvic fracture with severe hemorrhagic infiltration and hematoma of the pelvic muscles without arterial injury. Bone bleeding and the vascular damage associated with disruption of the sacroiliac ligaments promote a very significant bleeding. Simple maneuvers such as sheet circumferential compression to promote pelvic ring closure are effective on stabilizing and closure of the sacroiliac joint. Hip manipulation of the fracture was performed during the necropsy to demonstrate and prove how a simple sheet contention can promote stabilization of the pelvic ring by closing the sacroiliac joints in open book fractures.

Novel Method to Characterize and Model the Multiaxial Constitutive and Damage Response of Energetic Materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaneshige, Michael J.; Rabbi, Md Fazle; Kaneshige, Michael J.

2017-12-01

Simulant polymer bonded explosives are widely used to simulate the mechanical response of real energetic materials. In this paper, the fracture resistance of a simulant polymer bo nded explosive (PBX) is experimentally investigated. The simulant is composed of 80 wt.% soda lime glass beads (SLGB) and 20 wt.% high impact Polystyrene 825 (HIPS). Brazilian disk tests are performed to characterize the tensile and compressive properties. Fracture toughness and energy tests are performed in the semi - circular bending (SCB) configuration on 80, 81, 82, and 83 wt % SLGB compositions. Digital image correlation is performed to record the surface displacementsmore » and calculate surface strains during testing. The m icromechanical behavior of ductile and brittle fracture are evaluated using digital microscopy and scanning electron microscopy of the fracture surface. It is determined that (i) the manufacturing process produces a credible simulant of PBX properties, and (ii) the SCB test measures fracture resistance with a reasonable coefficient of variation.« less

On the mode I fracture analysis of cracked Brazilian disc using a digital image correlation method

NASA Astrophysics Data System (ADS)

Abshirini, Mohammad; Soltani, Nasser; Marashizadeh, Parisa

2016-03-01

Mode I of fracture of centrally cracked Brazilian disc was investigated experimentally using a digital image correlation (DIC) method. Experiments were performed on PMMA polymers subjected to diametric-compression load. The displacement fields were determined by a correlation between the reference and the deformed images captured before and during loading. The stress intensity factors were calculated by displacement fields using William's equation and the least square algorithm. The parameters involved in the accuracy of SIF calculation such as number of terms in William's equation and the region of analysis around the crack were discussed. The DIC results were compared with the numerical results available in literature and a very good agreement between them was observed. By extending the tests up to the critical state, mode I fracture toughness was determined by analyzing the image of specimen captured at the moment before fracture. The results showed that the digital image correlation was a reliable technique for the calculation of the fracture toughness of brittle materials.

Aging and loading rate effects on the mechanical behavior of equine bone

NASA Astrophysics Data System (ADS)

Kulin, Robb M.; Jiang, Fengchun; Vecchio, Kenneth S.

2008-06-01

Whether due to a sporting accident, high-speed impact, fall, or other catastrophic event, the majority of clinical bone fractures occur under dynamic loading conditions. However, although extensive research has been performed on the quasi-static fracture and mechanical behavior of bone to date, few high-quality studies on the fracture behavior of bone at high strain rates have been performed. Therefore, many questions remain regarding the material behavior, including not only the loading-rate-dependent response of bone, but also how this response varies with age. In this study, tests were performed on equine femoral bone taken post-mortem from donors 6 months to 28 years of age. Quasi-static and dynamic tests were performed to determine the fracture toughness and compressive mechanical behavior as a function of age at varying loading rates. Fracture paths were then analyzed using scanning confocal and scanning-electron microscopy techniques to assess the role of various microstructural features on toughening mechanisms.

[Direct osteosynthesis of instable Gehweiler Type III atlas fractures. Presentation of a dorsoventral osteosynthesis of instable atlas fractures while maintaining function].

PubMed

Böhm, H; Kayser, R; El Saghir, H; Heyde, C-E

2006-09-01

This retrospective study evaluates eight patients with unstable fractures of the atlas vertebra, treated operatively in the Central Clinic Bad Berka between January 1995 and December 2001. In all cases, we were confronted with unstable and dislocated type III fractures according to Gehweiler, caused by an injured transverse ligament. Mean age was 34 years (range 20-49) in two women and six men. We introduce a new technique of direct reconstruction of the atlas vertebra. This technique leads to a stable ring construct that allows compression osteosynthesis of the fracture. Spinal fusion can be avoided, as can postoperative immobilization, since sufficient stability for functional postoperative treatment is achievable. The follow-up control 38 months (range 6-75) after surgery showed solid bony fusion in all cases, in one case after revision surgery. All patients showed good functional results, there was no need for analgesics and all patients could be reintegrated into their former occupation.

USE OF COMPOSITE MATERIALS AS A COMPONENT OF TUSK FRACTURE MANAGEMENT IN AN ASIAN ELEPHANT (ELEPHAS MAXIMUS) AND AN AFRICAN ELEPHANT (LOXODONTA AFRICANA).

PubMed

Sim, Richard R; Stringer, Elizabeth; Donovan, Dennis; Chappell, Rachael; Flora, Pat; Hall, Jon; Pillay, Selvum; Willis, Benjamin G; McCain, Stephanie

2017-09-01

Tusk fractures in Asian (Elephas maximus) and African elephants (Loxodonta africana) can result in damage to the distal end or to longitudinal cracks, potentially progressing to pulpitis. With pulp exposure, endodontic therapy is the treatment of choice, but conservative therapy has sufficed for some elephants. This manuscript describes the use of composite materials as a component of tusk fracture management. A 7-yr-old male Asian elephant fractured the distal end of both tusks with pulp exposure in one. Capping of each tusk with a Kevlar/fiberglass composite prevented further damage, and a modification allowed care of the exposed pulp tissue. A 34-yr-old male African elephant with a longitudinal crack received a carbon fiber/fiberglass composite circumferential wrap to potentially stabilize the crack. Compression of the crack was achieved, but follow-up was truncated due to bacterial pulpitis. Both cases show that composite material allows for lightweight, durable management of tusk fractures with continued radiographic monitoring.